Awesome! Thank you, @kc1di and @Brickwizard! That worked.
For anyone in the same position, the commands that fixed it were (as root):
dkms remove rtl8812au/5.7.0 --all
dkms remove 8812au/18.104.22.168_35491.20191025 --all
dkms remove 8812au/22.214.171.124_37279.20201012 --all
We've recently moved, and the desktop my kids use is no longer accessible to ethernet. I've got an old Anewkodi USB Wifi adapter I'm trying to get working.
Based on reading other threads, I've tried adding the multiverse and universe repos, and installing `rtl8812au-dkms` (and rebooting...