This device failed.
- I could not login via LuCI (correct password brought you back to the login screen)
- after I SSHed to router and
reboot
the would not boot back up
I had to use the Emergency Room firmware recovery to downgrade to 19.07.9.
(Also, I don't recall doing this when I first switch to OpenWrt; but I had to use the Factory in Emergency Room, then flash again with sysupgrade after it booted. Otherwise it rebooted into the same unusable state - just FYI.)