Comment # 25 on bug 1132926 from Otrebor Igorig

I've tested with the 5.0.10 kernel from the Kernel:stable repo, and the issue
persists. There are very slight nuances in behaviour, but it still fails to
initialize the external monitor.

During the boot process the ext monitor seems to initialize properly multiple
times. This is true for the console screen as for the graphical screen when
entering the encryption keys for dm-crypt. However, it fails when switching to
the graphical login screen. I am also not able to activate it once I have
logged in.

I've also tried to undock the device and attach the screen directly to the
onboard DP of the device. This works as expected allthough it does limit the
resolution of the ext monitor to 2560x1440 instead of 3840x2160.