Tested with macOS 10.15.7 (Darwin v19.6.0), Xcode 12.1 build 12A7403, & packages from homebrew.
Tested with macOS 11.6 (Darwin v20.6.0) Xcode 13.0 build 13A233, arm64 kernel, & packages from homebrew.

• to view macOS version numbers, etc, run : sw_vers
• to view Darwin version numbers, etc, run : sysctl kern.osrelease

Brief/short info on macOS and Darwin Unix : macOS contains (BSD licensed, and) opensource Darwin² Unix based XNU hybrid core/kernel, & also contains Darwin unix as internal subsystem to support commandline based tools & functionalities. Darwin supports POSIX API because of its BSD unix based lineage and because of largely FreeBSD userland tools, etc. GUI layer is proprietary (not-opensource) licensed. Build tools need to be compatible with “darwin”.

• In macOS v10.15.x (Catalina) & earlier versions, the Kernel modules, hardware drivers, etc are known-as & usually loaded as kext (kernel extension) inside kernel space/layer, & uses LKM with KPI (kernel programming interface) & d-KPI¹ (deprecated-KPI). But, since macOS v11 (Big Sur) & newer versions, the newer sext/sysext (system extension) and (older) kext without d-KPI are used in user space/layer. And newer dext (driver extension) in macOS v11 & later also runs in user space/layout, and replaces earlier I/O kit. So hardware/software developer/MFR should still supply sext/dext & kext (without d-KPI).

Obtain build toolchain that is more suitable for Apple hardware & macOS & Darwin Unix.

• Install Xcode or CLT:
  1. Obtain Xcode¹ from here. Note: installer file download is over/near 5 GB, and needs 17+ GB space. Xcode 11.5 : 16,958,217,326 bytes (10.5 GB on disk).
     • to view installed Xcode version number, run this command : xcodebuild -version . If output not-showing version number then Xcode is not-installed.
  2. If you prefer to not obtain Xcode, then one of the alternative is:
     • obtain Command-Line-Tools¹ (CLT) from here, or Load it from App Store in macOS, or use below command, or obtain apple-gcc package via package manager software. CLT is also known as Command Line Developer Tools. Note: installer download is under/near 300 MB, and may need around ~ 2 GB space.
     • inside Terminal¹ utility/app, run this command to load CLT:

       xcode-select --install

       • to view installed CLT version number, run this command : pkgutil --pkg-info=com.apple.pkg.CLTools_Executables . If output not-showing verison number or showing msg that “...No receipt...” then CLT is not installed, or its bundled inside+with Xcode. To view pre-installed pkgs you may run : pkgutil --pkgs
         
         
• To view toolchain version numbers, directory, etc info, run this command:

  gcc -v && llvm-gcc -v && clang -v

• you may also run xcrun clang command, & see what it outputs:

  UserMacBook:~ username$  xcrun clang
  clang: error: no input files

  • if output is NOT this message clang: error: no input files, then either installation has error or executable files are not in PATH env var correctly.
    
    
• Build toolchain (Xcode or CLT) from apple is used (in first stage) to create a software components for openwrt build purpose, then (in second stage) those software components are used to create the final openwrt components, in order to create openwrt firmware, etc, that are widely compatible with cross-platform.

• We need to view full filename, file extensions, all files & directories, etc including hidden ones, very accurately, so that there is lesser mistakes.
• Use Finder to start Terminal¹ in macOS:
  
  • Finder is very similar to Windows-Explorer file-browser app/tool. In macOS > click on any empty area in Desktop screen > then in top-side  menu, click on Window > click on Bring All to Front > in left-pane (in left side column) of Finder, go under Favorites and click on the Applications > then scroll down & go into Utilities sub-folder > then click on Terminal or Terminal.app to start it. macOS Terminal is very similar to Windows Command-Prompt, a command-line interface (CLI) tool.
  • Hotkeys to start Finder instantly : [Alt/Option⌥] + [Command⌘] + [Space-bar] then close the Search tab.
  • Hotkeys to start Terminal instantly : None. ( Note: Keep Terminal running, after a reboot Terminal will auto-start if you check-marked the option: Load previous running apps after reboot ).
• Run below command inside Terminal:

  defaults write com.apple.Finder AppleShowAllFiles true

  • above only makes the files viewable inside file-browser software, it does not actually change any file-attributes.
    
    
• then you must reboot Mac-computer OR run (any one of the) below command:

  /usr/bin/sudo /usr/bin/killall Finder /System/Library/CoreServices/Finder.app

  or, run just this:

  /usr/bin/sudo /usr/bin/killall Finder

  or, just this:

  sudo killall Finder

• then Finder will auto start, and all hidden files+folders will by-default begin to be shown to user in macOS Finder.
• in macOS Finder or inside any other file browsing window in macOS, user can also press below THREE buttons altogether ONCE to show all HIDDEN files/folders:
  • [Command⌘] + [Shift⇧] + [.>]
  • if user press-es above three buttons again, file-browsing-window will HIDE the HIDDEN files/folders.
• By default in macOS, Finder will keep most of the file extension hidden. But we need to see all file's extension to see FULL filename, so we can be sure & not make mistake. To view all file's extension, do below steps:
  • in macOS > start “Finder” app > goto main menu > Finder > Preferences > Advanced > select the Show All Filename Extensions option.

Install any one of the (3rd-party) package manager (pkg-mngr) software in macOS:

1. Homebrew.
   • Warning : homebrew is opensource pkg-mngr but this tool is programmed by it's developers to share user's usage & private data with Ggl (including IP-address, which is private & tracking data), Ggl stores user's all data forever for whatever purpose they want to use it for^{1, 2}, homebrew also changes permission where it should avoid¹. Such mass scale data theft / collection activities are also supported + promoted by (official/unofficial) partners, supporters & enablers & software developers, etc. All of them are assisting & submitting private & tracking data into Ggl. So all of our all activities are digitally tracked / recorded, it means we are all inside digital jail, we are digitally arrested inside a digital jail, such activities are not only unconstitutional in USA, it is also violating international agreements & laws on human-rights, & creates more opportunity for mass scale crimes & violations.
     • if you use homebrew: then use OPT OUT option/command in homebrew, to opt out from their data collection/theft of your usage/personal data, and that is not enough, also load specific site connection blocker (to block Ggl Analytic, etc) configuration or settings in your computer or in your firewall app/rule or in your computer's hosts¹ file.
       • macOS (until 10.14.x macOS Mojave) uses /etc/hosts file, & macOS (10.15.x) Catalina uses /private/etc/hosts file.

         0.0.0.0 google-analytics.com
         0.0.0.0 www.google-analytics.com

       • sometime above hosts file based solution is not-enough : ip-addresses (and ranges) of Ggl Analytic site need to be blocked carefully via firewall rules, for specific app(s)/tool(s).
     • Most of the time, private data & private tracking-data theft / collection / recording by (Ggl, etc) search engine is not possible to block normally at all. Whenever you or an app/tool connects with (Ggl or other) search engine directly to search for something, then that (Ggl or other) search engine can collect / record ip-address, search string, app info, USER-AGENT info, etc various private & tracking data/info, and then some search engine company/corporation (in.example: Ggl) stores such private & tracking data permanently forever. So also see: 1, 2, eff.
       • so to overcome this type of mass-scale & human-rights violating data tracking & theft, you would need to use VPN-tunnel(s) or Tor-network or SSH-tunnel(s) based indirect connection into (Ggl) search engine. Search engine (in.example: Ggl) will still record/steal ip-address tracking (and other private) data but that will be VPN or Tor or SSH exit-point's ip-address.
     • do not encourage others to expand data theft or digital jail or more abuse. create barriers/obstacles for greedy monsters. Any private (or public) entity without all human's/people's direct oversight or accountability or punishment, is not a democratic & not a good / beneficial entity in the long run. And after creating obstacle for recording ip-address tracking data, we strongly request to you/user, that you/user also MUST not engage into any type of human-rights violating or criminal activities (like greedy monsters), you/user MUST have to uphold (good) moralities & ethics & humanity that is beneficial for ALL people/human, for earth/environment, etc, for now & future generations.
       
       
2. MacPorts : it is opensource & free pkg-mngr, & does not steal your usage/private data. MacPorts guide.
   • download/obtain MacPorts installer dmg/pkg file, install it. More info here.
   • Before MacPorts is installed, your ~/.bash_profile file (inside your home directory) may look close to like this:

     # .bash_profile for BASH
     # PROMPT_COMMAND=update_terminal_cwd
     PS1='\h:\W \u\$ '
     PS2='> '
     PS4='+ '
     PATH="/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin"
     export PATH

   • MacPorts installer webpage will instruct you to add macports pkg-mngr executable file locations in the end of your PATH variable, like this:

     PATH="$PATH:/opt/macports/bin:/opt/macports/sbin"

     • after you add above line manually in ~/.bash_profile file, it will look like below:

       # .bash_profile for BASH
       # PROMPT_COMMAND=update_terminal_cwd
       PS1='\h:\W \u\$ '
       PS2='> '
       PS4='+ '
       PATH="/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin"
       PATH="$PATH:/opt/macports/bin:/opt/macports/sbin"
       export PATH

     • you can use this command to edit the ~/.bash_profile file:

       sudo nano ~/.bash_profile

   • When MacPorts is installed, installer will add locations in PATH where macports port package executables are stored, inside the ~/.bash_profile file. In that way, your macOS user account can find+use the installed macports port package files, after you login. But we have to change it little bit.
     Here is what you will usually see in ~/.bash_profile file (after macports is installed):

     # .bash_profile for BASH
     # PROMPT_COMMAND=update_terminal_cwd
     PS1='\h:\W \u\$ '
     PS2='> '
     PS4='+ '
     PATH="/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin"
     PATH="$PATH:/opt/macports/bin:/opt/macports/sbin"
      
     ##
     # Your previous /Users/<YOUR-USER-NAME>/.bash_profile file was backed up as /Users/<YOUR-USER-NAME>/.bash_profile.macports-saved_2021-08-29_at_16:38:31
     ##
      
     # MacPorts Installer addition on 2021-08-29_at_16:38:31: adding an appropriate PATH variable for use with MacPorts.
     export PATH="/opt/local/bin:/opt/local/sbin:$PATH"
     # Finished adapting your PATH environment variable for use with MacPorts.

   • Change above codes, into below code:

     # .bash_profile for BASH
     # PROMPT_COMMAND=update_terminal_cwd
     PS1='\h:\W \u\$ '
     PS2='> '
     PS4='+ '
     PATH="/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin"
     PATH="$PATH:/opt/macports/bin:/opt/macports/sbin"
      
     ##
     # Your previous /Users/<YOUR-USER-NAME>/.bash_profile file was backed up as /Users/<YOUR-USER-NAME>/.bash_profile.macports-saved_2021-08-29_at_16:38:31
     ##
      
     # MacPorts Installer addition on 2021-08-29_at_16:38:31: adding an appropriate PATH variable for use with MacPorts.
     # export PATH="/opt/local/bin:/opt/local/sbin:$PATH"
     export PATH
     # Finished adapting your PATH environment variable for use with MacPorts.

   • in above we have disabled MacPorts based port package locations from PATH, but locations of MacPorts pkg-mngr itself are kept in PATH. The “PATH” is an essential environment variable which indicates the sequence of directories/folders where to look for a specific (executable) program. The changes we made, will allow newly installed (MacPorts) packages stay out of touch of other software which does not need to use them. These (MacPorts) packages are needed for development/build purpose of OpenWRT, so we will create a separate executable file (env.sh) to load PATH (and other build environment variables), which is suitable for using inside a shell-manager's specific shell TAB(s) only, for openwrt build/development purpose. See step/section F in below for details on creating this env.sh file.
     
     
3. pkgsrc : it is an opensource & free pkg-mngr (package-manager) for NetBSD unix OS, but can also be used by other OS, including macOS/darwin. Download: dev, Src: gh, More info: wp.

• Warning : macOS keeps the default PATH in /etc/paths file, but do not edit/change it, because such change can affect entire or many parts of macOS system. We only need to change build environment only for 1 or 2 shell instance(s), and not for entire macOS system, and also not for all other apps in macOS.

Create a dedicated case-sensitive filesystem for OpenWRT build/compile purpose:

• We will be using a sparsebundle to allow us to have a case sensitive filesystem.
• The size that you provide will be the max size of the volume for working with OpenWrt. Execute below commands inside a Terminal shell instance:

  cd ~
  hdiutil create -size 20g -type SPARSE -fs "Case-sensitive HFS+" -volname OpenWrt OpenWrt.sparseimage
  hdiutil attach OpenWrt.sparseimage

  • the command cd ~ in above is taking developer-user inside the HOME directory of user-account in macOS, then OpenWrt.sparseimage file is created there. But if you want to create the SPARSE image file in a different directory, then change the cd ~ line & go inside your preferred volume/directory.
    
    
• Optional/Informational:
  • if you want to open the OpenWRT Volume (aka: Drive, aka: Disk) after creating then use below command as 3rd-command line in above:

    hdiutil attach OpenWrt.sparseimage -autoopenrw

  • after a reboot, if OpenWRT volume is not available in your macOS, then run:

    cd ~ && hdiutil attach OpenWrt.sparseimage -autoopenrw

  • if you want to keep the OpenWRT volume always attached, then:

    cd ~ && sudo hdiutil attach OpenWrt.sparseimage -notremovable -autoopenrw

  • if you want to detach (aka: unmount) the OpenWRT volume, then:

    hdiutil detach /Volumes/OpenWrt

  • More info on hdiutil is here.

Go inside the OpenWRT build volume, with below command, in Terminal:

• cd /Volumes/OpenWrt

• Create a file called env.sh inside /Volumes/OpenWrt to indicate location of installed packages. It will also help us to create openwrt build friendly environment, inside a specific shell tab/instance in shell-manager software like Terminal.
  • This is to allow packages from pkg-mngr (which we will install in next step) to be used, instead of the macOS provided ones.
• For x86_64 Apple hardware, & when you have MacPorts, then create env.sh file with below content, save it inside /Volumes/OpenWrt location:

  env.sh

  #!/opt/local/bin/bash
  PS1='\h:\W \u\$ ';PS2='> ';PS4='+ ';
  # Bring PATH lines from the ~/.bash_profile file into below:
  PATH="/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin"
  PATH="$PATH:/opt/macports/bin:/opt/macports/sbin"
  # Adding path of macports port packages, in ahead of others:
  PATH="/opt/local/libexec/gnubin:/opt/local/bin:/opt/local/sbin:/opt/local/libexec:/opt/local/x86_64-apple-darwin19.6.0/bin:$PATH";
  # Load PATH into currently running shell:
  export PATH;
  # Load other environment variables:
  export JAVA_HOME=/Library/Java/JavaVirtualMachines/openjdk7-zulu/Contents/Home

  • turn the env.sh file an executable shell script file with this command:

    chmod +x /Volumes/OpenWrt/env.sh

  • For MacPorts create MacPorts.sh file in your home ~/ directory with this command:

    sudo nano ~/MacPorts.sh

  • find the PATH variables lines in your ~/.bash_profile file, and add into below content, then copy all from below & paste into ~/MacPorts.sh file. You can also download below code as a file, then change upper 2 PATH variables, to match with your PATH inside your ~/.bash_profile file:

    MacPorts.sh

    #!/opt/local/bin/bash
    PS1='\h:\W \u\$ ';PS2='> ';PS4='+ ';
    # Bring PATH lines from the ~/.bash_profile file into below:
    PATH="/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin"
    PATH="$PATH:/opt/macports/bin:/opt/macports/sbin"
    # Bring last PATH line from the /Volumes/OpenWrt/env.sh file into below:
    PATH="/opt/local/libexec/gnubin:/opt/local/bin:/opt/local/sbin:/opt/local/libexec:/opt/local/x86_64-apple-darwin19.6.0/bin:$PATH";
    # Load PATH into currently running shell program:
    export PATH;
    # Load other environment variables:
    export JAVA_HOME=/Library/Java/JavaVirtualMachines/openjdk7-zulu/Contents/Home

  • turn the MacPorts.sh file an executable shell script file with this command:

    chmod +x ~/MacPorts.sh

• For x86_64 Apple hardware, & when you have homebrew, then create env.sh file with below content:

  PATH="/usr/local/opt/make/libexec/gnubin:$PATH"
  PATH="/usr/local/opt/gnu-getopt/bin:$PATH"
  PATH="/usr/local/opt/gettext/bin:$PATH"
  PATH="/usr/local/opt/coreutils/libexec/gnubin:$PATH"
  PATH="/usr/local/opt/findutils/libexec/gnubin:$PATH"
  export PATH

• For arm64 (Apple Silicon(M1)) Apple hardware, & when you have homebrew, then create env.sh file with below content:

  PATH="/opt/homebrew/opt/make/libexec/gnubin:$PATH"
  PATH="/opt/homebrew/opt/gnu-getopt/bin:$PATH"
  PATH="/opt/homebrew/opt/gettext/bin:$PATH"
  PATH="/opt/homebrew/opt/coreutils/libexec/gnubin:$PATH"
  PATH="/opt/homebrew/opt/findutils/libexec/gnubin:$PATH"
  export PATH

• Optional : you may check homebrew official page or MacPorts-guide if you need more information related to PATH variable, or other info on pkg-mngr.
• Optional : turn env.sh file an executable shell script file: chmod +x /Volumes/OpenWrt/env.sh

Install necessary packages via pkg-mngr, packages which help to build openwrt components. Use below commands inside a shell instance/tab in Terminal. Note: Packages will be installed inside macOS default volume, not inside /Volumes/OpenWrt

• if you have homebrew pkg-mngr then run this command:

  brew install coreutils findutils gawk grep gnu-getopt gnu-tar wget diffutils git-extras quilt svn make ncurses pkg-config

  • in above, homebrew command does not include the pre-requisites (aka: dependencies) packages mentioned here.
    
    
• if you have MacPorts pkg-mngr then run below 2 commands:

  source ~/MacPorts.sh
  sudo port install libiconv gettext-runtime coreutils findutils gwhich gawk zlib pcre bzip2 ncurses grep getopt gettext-tools-libs gettext diffutils sharutils util-linux libxslt libxml2 help2man readline gtime gnutar unzip zip lzma xz libelf fastjar libusb libftdi0 expat sqlite3 openssl3 openssl kerberos5 dbus lz4 libunistring nettle icu gnutls p11-kit wget quilt subversion gmake pkgconfig libzip cdrtools ccache curl xxhashlib rsync libidn perl5 p5.28-xml-parser p5.30-xml-parser p5-extutils-makemaker p5-data-dumper boost-jam boost boost-build bash bash-completion binutils m4 flex intltool patchutils swig git-extras git openjdk17 openjdk7-zulu luajit libtool glib2 file python27 python310 libzzip mercurial asciidoc sdcc gnu-classpath

  • in above, MacPorts command includes the pre-requisites (aka: dependencies) packages mentioned here. Space initially used by all of these packages : 4,190,442,792 bytes (2.57 GB on disk) for 129,623 items, (as of March-11, 2022). Note: As different packages are continuously modified & improved by their devs or releaser or adopter or maintainer, so their occupying space size & items count will be different in your computer in different time.
    
    
  • if you need picocom tool to communicate with router via serial adapter/cable¹ connection, then:

    sudo port install picocom

  • if you need last stable openssh (aka: ssh), sftp, scp tools for secure communication or file-transfer, then:

    sudo port install openssh

  • if you need TFTP daemon/server (tftpd) to receive files from router, then:

    sudo port install tftp-hpa

  • if you need to use last stable telnet¹, ftp, rsh, rlogin, tftp¹ tools and corresponding daemons/servers, then:

    sudo port install inetutils

    • if you need other type of bundled packages, then look here: 1.
      
      
  • if you need these type of tools, (more info: 1), then:

    sudo port install arm-elf-binutils i386-elf-binutils m68k-elf-binutils mips-elf-binutils x86_64-elf-binutils

macOS by default uses a very old version of bash shell. So, we can+should start a build/compile friendly common last+stable or recent version of bash shell inside macOS-Terminal's specific tab, as such recent version can be obtained & used by most developer users. Shell-manager software Terminal can run multiple shell instances, by using multiple Terminal-tabs. Select one (or more) Terminal-tab(s) to use for openwrt build purpose, then run below command to have same (last+stable) build environment.

• If you installed new bash package, then start new bash shell inside a specific tab in Terminal, (when you have MacPorts based bash package), with this command:

  exec /opt/local/bin/bash

  • optional : approve/permit new bash shell in macOS with this command: echo “/opt/local/bin/bash” | sudo tee -a /private/etc/shells
  • optional : if you want to continue to use the new bash always, then: click on apple  symbol in topside apple menu-bar > System Preferences... > Users & Groups > Unlock the 🔒pane > control click on your user-name > select Advanced Options... > then update/change the Login shell into /opt/local/bin/bash > ok.

We need to load build package locations indicator file as shell environment. OpenWRT developing (aka: building, aka: compiling, aka: compilation) is done inside a suitable (aka: build friendly) shell environment. So, we have to allow openwrt build commands to find packages that we installed via pkg-mngr, by loading build package location indicator file env.sh into one of the Terminal shell environment tab, to create that openwrt build friendly & suitable shell environment.

• When developing (aka: building, aka: compiling), run below command to set up build-friendly PATH (and other) variable(s). This leaves your system in a clean state without symlinking.

  source /Volumes/OpenWrt/env.sh

  • Optional : So from next time or after a reboot, when you want to enter into openwrt build mode, then run below 2 commands inside a specific tab in Terminal, when you have MacPorts based bash package:

    exec /opt/local/bin/bash
    source /Volumes/OpenWrt/env.sh

Now proceed normally, (that is, start to follow build related other steps/procedures, shown in parent/previous page).

Users who are developing openwrt firmware for Broadcom (BCM) 43xx chipset, need this b43-fwcutter tool to extract wireless drivers from firmware.

• More info here.
• Package manager homebrew has this tool, and MacPorts does not.
  • Users of MacPorts can obtain source^{1, 2, 3, 4} & compile, or get it¹ from FreeBSD pkg.

Golang¹: For darwin/arm64 and linux/aarch64 golang package (feed “packages”) golang C-bootstrap method doesn't work, but it is possible to use external golang bootstrap. On MacOS arm64 the easiest way is to install golang using brew and use installed golang as bootstrap:

• brew install golang

• Then set CONFIG_GOLANG_EXTERNAL_BOOTSTRAP_ROOT=“/opt/homebrew/opt/go/libexec” in .config file

No need to install these, unless you specifically need such tool/app/utility to assist your build related works. Here is a small list of some optional/extra tools related to openwrt software code build & test & usage & diagnostics, etc, and also list of some optional/extra tools related to network device test/diagnostics, etc to run/use in macOS (apple macintosh operating system) and apple hardware. For more, goto wp.

• XQuartz (dev, wp, src, dnld) : it allows cross-platform (GNU-Linux, etc) apps/tools (which were developed to use X11 GUI), to run on macOS & use macOS's native Quartz GUI, etc. Many GUI apps/tools need this. It is opensource tool.
• PeaZip (dev, dnld, src, wp, comparison) : it is a free & opensource archiver (zip, compress) & unarchiver (unzip, decompress) app/tool. GUI (Graphical User Interface) based. Allows to create: 7Z, ARC, Brotli, BZ2 (BZip), GZ (GZip), PAQ/ZPAQ, PEA, QUAD/BALZ/BCM, sfx, TAR, WIM, XZ, ZPAQ, ZIP, Zstandard, etc, and peazip allows to Open & Extract 200+ file types: ACE, CAB, DEB, ISO, RAR, UDF, ZIPX, etc.
• GnuPG for OSX (dev, dnld) : verifies file's/message's authenticity. GnuPG is aka (also known as) GPG. We need this tool to verify/authenticate downloaded files (or messages) to find-out whether files (or messages) are indeed what actual file (or message) creator/author/developer actually released/shared/created/sent, So this tool will indicate/tell us whether received files (or messages) were modified/altered/changed/abused/corrupted by someone or some-device in the middle of file/msg travel path or during file/msg travel path, or this tool will indicate to us NO modification was done during file/msg travel path. File's (or message's) actual creator/developer shares their (GnuPG/GPG or PGP or OpenPGP based) crypto (cryptographic) digital pub-key file as pub file or as asc file with public. Most trustworthy way to obtain such pub-key is: goto a KSP or conference and meet actual file/msg creator/developer & obtain pub-key file directly, (or else, the next (slightly-less) trustworthy solution is: use WoT & inspect pub-key components to compare & verify a pub-key's authenticity). File/msg creator/developer signs main-file (or main-msg) with their prv-key, & that creates an unique sig (signature) file for a main-file (or main-msg), then file/msg creator/dev shares main-file (or main-msg) & sig-file with public. This (GnuPG) tool can use sig-file, pub-key file, & main-file (or main-msg), & can indicate if the main-file (or main-msg) was actually released by the actual holder of the pub-key, or not. Install a GUI frontend / wrapper for this tool.
  • to know directory location of installed gpg2 which your system will find (via PATH env var) & use, run : which gpg2
  • the GnuPG tool can also be loaded via MacPorts pkg-mngr, when you run this command : sudo port install gnupg2
  • GpgFrontend (dev, src, dnld) : opensource, free tool to authenticate file, to authenticate message, etc. it contains OpenPGP crypto tool and can also function as a frontend / wrapper for GnuPG. See GnuPG for OSX item in above.
• DevUtils (dev, dnld, appstore) : it has various functionalities to perform various development related activities. App is free & opensource, but source-code requires a payment.
  • Various tools/apps for Build, Deployment, etc are here: 1.
• TimeUTC (AppStore) : it can add a second date & clock in your topside apple  menu bar, to display current UTC time & date. freeware.
• FileZilla (dev, dnld, src, comparison) : it is a client app for FTP, FTP over TLS (FTPS), SFTP SSH, SFTP. Opensource & free & GUI based.
• ProFTPD (dev, dnld, src) : For FTP / FTPS / SFTP server. opensource & free.
  • And also get web (GUI) based admin interface app proFTPd-admin (from here) for ProFTPD.
• Github Desktop for Mac (dev) : allows a developer user to access & collaborate & develop software, etc on Github.com site. GUI based free app.
• TextMate (dev, dnld, comparison) : a text editor. Opensource & GUI based free app. Few features : multi tabs, multi windows, regex based search & replacement, etc.
• Kate (dev, dnld) : opensource & free code/text editor.
• LuLu (dev) : it is GUI based & free & opensource firewall app to control outbound internet data traffic of apps/tools in macOS.
• Loading (dev) : it can show a spinning progress wheel in  menu bar when network is being used by app/tool. Clicking the icon can show the apps/tools that are using network, & holding down the option key can show individual processes. Opensource, free & GUI based tool.
• OpenSSH (Portable) (dev, src, dnld-src, comparison) : opensource & free. it is a remote-access client tool to connect with SSH-servers¹. It can encrypt all traffic into SSH-server to eliminate eavesdropping, connection hijacking, and other attacks, it has large suite of secure tunneling capabilities, several authentication methods, and sophisticated configuration options. Includes ssh, scp, sftp¹, ssh-add, ssh-agent, ssh-keygen, ssh-keyscan. Source can be compiled/built in macOS, or download openssh from macports pkg-mngr, or download dependencies via macports & then build/compile. CLI based. Get a GUI wrapper / frontend for this tool.
• Fugu (dev, src-2, wp) : a free & opensource & GUI based frontend / wrapper for OpenSSH ssh,sftp,scp, etc commandline tools. Very old, but still useful to handle SSH keys, etc. It is a SFTP client, SSH app.
• PuTTY (dev, wp, src, comparison) : it is a free & open-source terminal emulator, serial console and network file transfer tool, & supports several network protocols: SCP, SSH, Telnet, rlogin, and raw socket connection. Actually developed for Windows OS, but has been ported into MacPorts pkg-mngr to use in macOS. GUI based. To install via Macports pkg-mngr, run: sudo port install putty
  • PuTTY in MacPorts needs these dependencies (these wil be auto-loaded by macports): pkgconfig, gtk2. And gtk2 needs these dependenicies: gtk-doc, pkgconfig, perl5, autoconf, automake, libtool, xz, atk, pango, gdk-pixbuf2, gobject-introspection, xorg-libXi, xorg-libXrandr, xorg-libXcursor, xorg-libXinerama, xorg-libXdamage, xorg-libXcomposite, xorg-libXfixes, shared-mime-info, hicolor-icon-theme.
• Coccinellida (dev, dnld) : a simple SSH tunnel manager app. opensource, free. GUI based.
• STM (SSH Tunnel Manager) (dev, doc, appstore) : it can manage multiple ssh tunnels / connections: local, remote, socks-proxy, etc. it is a GUI based fronend / wrapper for ssh tool, but for socks-proxy it can use builtin ssh on some situations. freeware. not-opensource. GUI based & also frontend for SSH.
• OpenVPN Connect (dev, dnld, appstore, community-dnld, wp) : opensource & free. VPN (virtual private network) connector client tool. GUI based. (There are many other types of VPN¹ connector client/server app/tool).
• TunnelBlick (dev) : a free & opensource & GUI based frontend / wrapper for OpenVPN commandline tool.
• WireShark (dev, dnld, src, comparison, wiki) : it is a network data packet analyzer (aka: network protocol analyzer = NPA) software. Opensource, free & GUI based.
• VirtualBox (dev, dnld, comparison²) : a free & opensource & GUI based virtualizer software (from Oracle) to create (software based) virtual-machine (VM) inside a hardware based host machine. So with this app, user can run+use multiple+different operating systems (OS) simultaneously. User can create VM as client, VM as server, client+server VM, Desktop OS VM, Mobile OS VM, etc, etc. First version used codes from QEMU. It can emulate these (hardware) architectures as VM: x86, x86-64.
• QEMU (dev, dnld, src, wp) : it is free & opensource. It is a generic & open source machine emulator and virtualizer. It can emulate various (hardware) architectures as VM, such as: x86, x86-64, MIPS64 (up to Release 6), SPARC (sun4m and sun4u) (32/64), ARM (Integrator/CP and Versatile/PB), SuperH, PowerPC (PReP and Power Macintosh), ETRAX CRIS, MicroBlaze, and RISC-V, OpenRisc32, Alpha, LM32, M68k, S/390, SH4, Unicore32, Xtensa, etc.
• NTFS for Mac (Microsoft NTFS for Mac By Tuxera) (dev) : The functionality or ability to read NTFS partitions inside macOS is very helpful feature to transfer file(s) between NTFS partition HDD/SSD and your APFS (apple macOS file-system). This “NTFS for Mac” by Tuxera tool is not free (aka: as freedom of software), it is proprietary tool. Only trial version is freeware for 15days, tiral version has some helpful functionalities. Full functionalities (after 15 days trial) requires a payment.
  • HDD/SSD storage device MFR (aka: manufacturers) also includes NTFS for Mac (NTFS for Mac By Paragon¹, etc) software for macOS, with their some HDD/SSD storage device, So if your HDD/SSD drive (in your computer) matches with MFR's HDD/SSD then you may use that NTFS for Mac software (by obtaining it from HDD/SSD MFR's website).
  • Earlier helpful software FUSE for macOS^{1, 2, 3} is not anymore free (as in freedom of software) for macOS, it is now proprietary for macOS. The Mounty for NTFS¹ and NTFS-3G^{1, 2} are free & opensource, but slow. Linux kernel v5.15 & onward has began to support NTFS¹ 3.1 & earlier versions, NTFS driver was provided by Paragon.
• Deluge (dev, dnld, comparison) : a bittorrent network based file-sharing software. free & opensource. Encrypt or Password protect files before sharing, & share password via a separate (private) channel. Filename can have contact info if you wish to be contacted, but remember that such contact info will also be abused by someone out there. More info here.
• Thunderbird (dev, dnld, src, comparison) : multi data communication-protocol supporting client, but more commonly known as an Email client app (for viewing, reading, sending emails), so it is a PIM¹/PDM¹ client (that supports personal/private information like: emails, address-book, calendar dates, emails, instant messages, passwords, alerts, browsing site data, etc, etc). Thunderbird is free & opensource. It is also client app/tool for: newsfeeds¹/newsgroups^{1, 2} (NNTP¹ client, NNTPS) , web feeds^{1, 2} (news aggregators¹, like: Atom¹, RSS¹, etc) client, instant messaging¹ (aka: chat¹ networks, like IRC¹, XMPP¹, Google-Talk, Twitter, Odnoklassniki, etc) client, address auto-completion (LDAP) client, etc. Thunderbird contains core/engine of Mozilla Firefox web-browser, which allows thunderbird to connect with various types of web-servers / web-sites to use various web-services, as a HTTP/HTTPS, & other protocols cleints, and firefox web-browser core also allows thunderbird to open^{1, 2, 3} multiple web-browser tab(s) (inside thunderbird) to be used by users, manually. Send yourself email (or chat-msg) with URL-links to various web-site services, then inside thinderbird right-click on link (inside email or chat-msg) & select the option to open the link inside a New Tab inside thunderbird¹, in this way you can use/access various WebMails^{1, 2}, Twitter¹, etc. More info on how to approve cookies & JS for such web-service website and dependent 3rd-party web-services (inside thunderbird), are explained here. Thunderbird addons can also allow access to various web-services more easily: Google-Chat¹, Skype-WebApp¹, Telegram-Web^{1, 2}. This type of app is very helpful to keep multi channel communications with openwrt & other various project developers, and to test your own servers. Get firefox addon uBlock Origin¹, & load into Thunderbird, that addon allows you to stop un-approved Advertisements that are using+stealing your computing (CPU, GPU, etc) resources, & (limited & costly) data allotments from your ISP, etc, without your consent/permission/approval.
• Apparency (dev, dnld) : it can inspect software application bundles (pkg, app, etc) for macOS, & then it can show info on code signing requirements, notarization, signatures, included frameworks, etc. it is a freeware.
• AppCleaner (dev) : open Finder > goto Application in any finder-tab > open this AppCleaner app, then drag the app that you want to remove/uninstall from Application folder/directory, & drop it inside the AppCleaner, it will inspect & find-out & show all elements used by that unwanted app, & also show you option to Remove. it is freeware.