Ubuntu 20.04 user not listed to login

Solution 1:

I had the same issue.

To fix that I did these steps in a terminal:

• sudo su we need to be superuser
• cd /var/lib/AccountsService/users here we go to the service that shows users, issue is here (at least in my case)
• you should see multiple files, one for each of your users, including the old one that is not showed in your screen. In this file check the value of SystemAccount. If it's true, then this is the issue: it should be false.
• if it does not help you, simply check differences between users files, the one that works with ones that don't. Also check that Icon path is correct.
• don't forget to exit su, and reboot after each try. Good luck, it took 3h digging before a fixed my issue.