The issue is my password becomes incorrect. If I use ctrl+alt+f3 to open a terminal and input my user name(checked the user name in recovery mode ls \home) and I am 100% sure my PW is correct since I can log in before the upgrade.
The error message I have is Login incorrect plus after a minute or 2, the terminal will reset. It looks like a login loop.
There are similar questions asked here.
Cannot login 20.04 LTS login loop
Log in fails and returns to log in screen
but none of them can resolve the issue I am having.
Any suggestions?
It could be your filesystem permissions getting messed up, or your keyboard layout going back to the default (causing a password with special characters to not work).
Either way, the first thing to try would be to reset your password in the recovery mode and see if you can log in with the new password.