I'm running Ubuntu 18.04 on a Lenovo X1 Yoga with touchscreen capabilities. When I rotate the laptop to portrait mode, the screen just goes black. When I rotate back to landscape, the screen returns.
EDIT: Just found out this only happens in Wayland, X seems to work fine. The issue in this post seems to be the same as my issue: 18.04 Ubuntu with Wayland, screen will not display in portrait
Solved updating to Ubuntu 18.10.
I can now pick-up the laptop, rotate it to portrait mode and the screen follows.