Comment 1 for bug 1756511

This happens to me too. Bionic freezes on the splash screen. I can get in via recovery mode but that's it. Also this guy on Ask Ubuntu has a similar Xorg.0.log where at the end the power button, keyboard, and mouse get removed.

https://askubuntu.com/questions/1029384/can-not-start-xorg-after-upgrade-ubuntu-to-18-04