I was having the same problem, but went for a different solution:
I noticed that if I created a new user the login of that user went fine. I assumed then the problem was in my user config.
So I made a backup of my home folder and removed my original user.
Then I created it again and login was successful. Of course I have lost all my configs, but the programs were still installed. Then I started to copy back folder by folder from my backup home to my new, clean, home.
I narrowed down the issue to the gnome extensions folder. As soon as I copied it back, the login loop happened again. I can't tell which extension was causing the issue, because I removed the extensions folder and reinstalled them using Chrome.
the folder location is:
Hope this helps users that had this issue. It was quite painful to see a LTS block in that way.