At least for me... how to get 21.02.0 (or 21.02.0rc4) on a WAC124.
The direct upgrade to rc4 or to final release 21.02.0 did not go well. In each case the wac124 would
give out DHCP, but have no open ports (SSH, HTTP, HTTPS) and so was useless.
Even using nmrp util to reinstall the official firmware and then load the 'factory'
images did not work. This was repeatable.
nrmp (this is very useful): https://github.com/jclehner/nmrpflash
If you find yourself in that situation:
0: Backup your config (before you get to this point.)
1: Use NMRP to install official 1.0.4.2 release (.6 also works, but gives a warning)
2: Login in (w/o a cable connected on the WAN side - obnoxious NetGear wants a relationship with you), set a pw and go to Advanced -> Admin -> Firmware and load 21.02.0rc3 - it must be rc3 (or earlier - not rc4 or final)
3: reboot, set up enough to log in.
4: wget (or scp) the 21.02.0 sysupgrade image to /tmp
5: use the standard 'sysupgrade -n imagefile'. This well blow away your config (the -n is needed)
Hope this helps someone.