I think I got hit by this bug too after the kernel update to 4.15.0-24-generic. Found this on askubuntu https://askubuntu.com/questions/1051555/after-security-update- to-4-15-0-24-generic-26-ubuntu-screen-shows-log-content which solves the problem.
Switcing to another tty and then switching to lightdm solved. -- You received this bug notification because you are a member of Ubuntu Desktop Bugs, which is subscribed to gdm3 in Ubuntu. https://bugs.launchpad.net/bugs/1779476 Title: Ubuntu 18.04: gdm3 does not switch to graphics after update To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gdm3/+bug/1779476/+subscriptions -- desktop-bugs mailing list email@example.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs