Always loopback into loginscreen: How do I fix it? (Ubuntu 18.04, gdm3)

Question

Installed a fresh 18.04 on a Lenovo T440. After 2 days, Ubuntu presents me a loopback into login screen every time I try to login.

ALT + STRG + F2 brings me into console, where I can proceed with login and startx brings me into a blank desktop environment, where some stuff is missing (this is unity-like taskbar thing for example).

Tried sudo apt-get install --reinstall ubuntu-desktop and sudo dpkg-reconfigure gdm3. Nothing.

service gdm3 restart just gets me back into loginscreen, where the problem persists.

How can I fix this? Is this known as a bug of some kind? Is there a failsafe display manager for older hardware on 18.04?

I would be ok with using another dm if there is no other way to fix this. I just need something stable. Used unity (16.04) and / or mate environment (mint) till now. First time with gdm3..

Edit: Output of gdm.service (logged in with "gnome" after installing "gnome" as dm - see answer below)

● gdm.service - GNOME Display Manager
   Loaded: loaded (/lib/systemd/system/gdm.service; static; vendor preset: enabled)
   Active: active (running) since Wed 2020-03-04 10:07:29 CET; 13min ago
  Process: 1009 ExecStartPre=/usr/share/gdm/generate-config (code=exited, status=0/SUCCESS)
 Main PID: 1011 (gdm3)
    Tasks: 3 (limit: 4291)
   CGroup: /system.slice/gdm.service
           └─1011 /usr/sbin/gdm3

Mär 04 10:07:29 x-ThinkPad-T440 systemd[1]: Starting GNOME Display Manager...
Mär 04 10:07:29 x-ThinkPad-T440 systemd[1]: Started GNOME Display Manager.
Mär 04 10:07:29 x-ThinkPad-T440 gdm-launch-environment][1023]: pam_unix(gdm-launch-environment:session): session opened for user gdm by (uid=0)
Mär 04 10:07:37 x-ThinkPad-T440 gdm-password][1349]: PAM unable to dlopen(pam_gnome_keyring.so): /lib/security/pam_gnome_keyring.so: Kann die Shared-Object-Datei nicht öffn
Mär 04 10:07:37 x-ThinkPad-T440 gdm-password][1349]: PAM adding faulty module: pam_gnome_keyring.so
Mär 04 10:07:39 x-ThinkPad-T440 gdm-password][1349]: pam_unix(gdm-password:session): session opened for user x by (uid=0)
Mär 04 10:07:44 x-ThinkPad-T440 gdm-launch-environment][1876]: pam_unix(gdm-launch-environment:session): session opened for user gdm by (uid=0)
Mär 04 10:10:14 x-ThinkPad-T440 gdm-password][2042]: PAM unable to dlopen(pam_gnome_keyring.so): /lib/security/pam_gnome_keyring.so: Kann die Shared-Object-Datei nicht öffn
Mär 04 10:10:14 x-ThinkPad-T440 gdm-password][2042]: PAM adding faulty module: pam_gnome_keyring.so
Mär 04 10:10:23 x-ThinkPad-T440 gdm-password][2042]: pam_unix(gdm-password:session): session opened for user x by (uid=0)

Answer 1

It could happen because of:

• Drivers have been screwed up
• User config files have been screwed up
• Ubuntu desktop config files or packages have been screwed up
• Newer kernel has a bug or doesn't support some drivers modules
• Some hardware issue exists

To eliminate the issue you could try:

• Drivers reinstalling
• Create new user and check if it works
• Purging ubuntu-desktop using sudo apt purge ubuntu-desktop && sudo apt purge *-gnome-*
• Loading from older kernel or install older kernel and boot with it
• Try to replace graphics card if it is possible and check with it

If you use Intel graphics drivers, it claims:

As the only industry-certified fully open source graphics driver, Intel's graphics drivers are already integrated into all popular Linux distributions, which means you’ll get the latest advancements without ever needing to install a separate driver. We develop this driver in collaboration with a community of developers around the industry based on standard specifications from the Khronos Industry Consortium*. Our operating system (OS) partners seamlessly integrate the driver into their OS in a way that every system with Intel graphics can display every detail, every shadow, and every animation in vivid 3D.

Answer 2

Did this: sudo apt install ubuntu-gnome-desktop, now I can login with gnome. Meh workaround.