I am experiencing the same problem. When I boot with any other kernel than 4.15.0-20-generic the internal display goes black after GRUB.
IMPORTANT: External display through USB-C works fine.
* Dell XPS 13 9350 Developer Edition.
* Ubuntu 18.04 (fresh install).
* Any other kernel than 4.15.0-20-generic.
* Internal display goes black, external display works fine.
* Switching VT does not turn the screen on.
* Adjusting backlight does nothing.
* Changing resolution does nothing.
I am experiencing the same problem. When I boot with any other kernel than 4.15.0-20-generic the internal display goes black after GRUB.
IMPORTANT: External display through USB-C works fine.
* Dell XPS 13 9350 Developer Edition.
* Ubuntu 18.04 (fresh install).
* Any other kernel than 4.15.0-20-generic.
* Internal display goes black, external display works fine.
* Switching VT does not turn the screen on.
* Adjusting backlight does nothing.
* Changing resolution does nothing.