NETGEAR R6230
The R6230 is most likely internally identical to the R6220. OpenWrt installation has been achieved by treating the device as an R6220. Although success has been achieved on two units, the R6230 is not officially supported.
For OpenWrt installation, please follow the instructions of Netgear R6220.
Installation of http://downloads.openwrt.org/releases/19.07.7/targets/ramips/mt7621/openwrt-19.07.7-ramips-mt7621-r6220-squashfs-factory.img via the OEM GUI was successful as documented for the R6220 despite warning that the OpenWrt firmware version (V1.0.0.86) was older than the OEM firmware (V1.1.0.86).