I have a Dell XPS 15 that had 20.04 installed with a separate partition for /home. This system had the problem, reported here some time ago, that required two attempts to login in to be successful.
Anyway, clean install 21.10 (formatted / but not /home) on it and guess what, every attempt to login in looped back to the login screen. Did another install of 21.10 but this time I created a new user and the install worked correctly. So, there is something in the original /home/user folder that was causing trouble.
My question is; rather than blowing away the complete /home/user folder is there something I can delete in the original folder that might fix this?