I got stuck in a Login-Loop. The solution with the .Xauthority permission would not fix it. Next i read about a lightdm bug. Since new ubuntu is using not lightdm but gdm3 i sudo apt-get purge gdm3 . Then reinstalled. After that i could login successfully.

[Tim Heusser]

New upgrade failed with initial upgrade and i had to boot-repair to get to the normal ubuntu login window.
The button Automatic Login in the settings does not work either...

Using Ubuntu 19.10

gdm3:
  Installed: 3.34.1-1ubuntu1
  Candidate: 3.34.1-1ubuntu1
  Version table:
 *** 3.34.1-1ubuntu1 500
        500 http://ch.archive.ubuntu.com/ubuntu eoan/main amd64 Packages
        100 /var/lib/dpkg/status

After a few Logins the bug reappeared and i had to reinstall the gdm3 package once again.

ProblemType: Bug
DistroRelease: Ubuntu 19.10
Package: gdm3 3.34.1-1ubuntu1
ProcVersionSignature: Ubuntu 5.3.0-19.20-generic 5.3.1
Uname: Linux 5.3.0-19-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.11-0ubuntu8
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Sat Oct 26 16:42:18 2019
InstallationDate: Installed on 2018-09-23 (398 days ago)
InstallationMedia: Ubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725)
SourcePackage: gdm3
UpgradeStatus: No upgrade log present (probably fresh install)

[Daniel van Vugt (vanvugt)]

Are you using automatic login or password login?

[Tim Heusser (timgravity)]

I'm using autologin. But the login-window always comes up wen booting into ubuntu.
The one where you can click your own user or login with a guest. (Page is all purple)
When booting into the recovery option everything works perfectly and the password prompt only comes up when i'm opening the browser and i can use the system normally.

[Daniel van Vugt (vanvugt)]

This sounds like bug 1845801 so we should probably treat it as a duplicate of that unless proven otherwise.

[Pranab Dhar (pkdhar)]

I have been struggling with this issue.
 1. I tried using "nomodeset" in grub, it didnt work.
 2. I tried replacing gdm3 with lightdm, that too did not work.

I am using the ubuntu driver NVIDIA-SMI 435.21 Driver Version: 435.21 CUDA Version: 10.1 on AMD 3960x cpu with kernel option mce=off.

This happens after i update the base OS installation with the new kernel and other additions.

Something is really broken as I have tried all the available options i could read about this issue. After 5 new installs it is the same story. I am now avoiding any updates for sometime to come.

[Compiler (pranav.bhattarai)]

I am currently having this issue.
The issue = Login Loop.

Distro: Ubuntu 19.10

As a temporary solution, I am using Lightdm instead of default GDM3.
Is there anything that I can help, do let me know.

[Nille (nille02)]

Nice, over half a year and it still persists. I have the same troubles with 20.04.