I was having the same issue. I discovered the issue when I found errors written to `/var/log/seat0-greeter.log`:
Error writing X authority: Failed to open X authority /var/lib/lightdm/.Xauthority: No such file or directory Indeed, I only had `/var/lib/lightdm-data`. Running the command mkdir /var/lib/lightdm and rebooting fixed the issue for me. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1473149 Title: Lightdm refuses to work after installing kubuntu-desktop To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/lightdm/+bug/1473149/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs