Unable to log in after 20.04 upgrade
After checking some more, I found that the upgrade from 18.04 to 20.04 (without formatting /home and /opt directories) had actually clobbered all permissions in the home directory. In particular, the .local directory was not writeable, which is probably why the login was hanging.
I've chowned the files to my username, and now the login is working. Since I used a recursive chown from the /home directory, I'm not sure if there would be any side effects, but at least login works.