mircea:

I followed the following instructions:

1. https://openwrt.org/toh/hwdata/mikrotik/mikrotik_rb931-2nd_hap_mini 2
2. https://git.openwrt.org/?p=openwrt/openwrt.git;a=commit;h=c2d2647c099679d64c8d5ef5260ba0f9d4c8f2ba

Using latest initramfs snapshot image as of today:
openwrt-ar71xx-mikrotik-rb-nor-flash-16M-initramfs-kernel.bin

root@OpenWrt:# cat /tmp/sysinfo/model
MikroTik RouterBOARD 931-2nD r2
root@OpenWrt:# cat /tmp/sysinfo/board_name
unknown
root@OpenWrt:# sysupgrade /tmp/fw.bin
Device unknown not supported by this image
Supported devices: rb-750-r2 rb-750up-r2 rb-750p-pbr2 rb-911-2hn rb-911-5hn rb-931-2nd rb-941-2nd rb-951ui-2nd rb-952ui-5ac2nd rb-962uigs-5hact2hnt rb-lhg-5nd rb-map-2nd rb-mapl-2nd rb-wap-2nd rb-wapr-2nd
Image check 'fwtool_check_image' failed.
root@OpenWrt:# echo rb-931-2nd > /tmp/sysinfo/board_name && sysupgrade /tmp/fw.bin
Cannot save config while running from ramdisk.
Commencing upgrade. Closing all shell sessions.

... upgrade then completes


There seem to be two peculiarities: board_name is "unknown" and model
has an extra "r2". (Thibaut, the developer who committed the code said
his router model does not contain "r2").

Extra information: forcing an upgrade while board_name is "unknown"
results in a broken upgrade, i.e. an infinite reboot loop.