Ubuntu 18.04 Black Screen after Blanking Screen
Solution 1:
Andrew. I experienced something similar to what you're getting. I have 18.04 with Linux 4.15.0-29-generic. This started to happen to me after I did install Nvidia Proprietary Drivers. If you updated from 16.04 where you were using proprietary drivers it can be the problem.
I would suggest to remove all the "Nvidia" drivers.
sudo apt-get --purge remove nvidia*
And maybe reconfigure X server.
sudo service gdm3 stop
sudo dpkg-reconfigure xserver-xorg
Helped me. Had it working with Nouveau.