Impossible to drive 144hz external monitor via USB-C (DP alt mode)

I'm not able to drive my external montior (144hz ultrawide) over a USB-C DP alt mode connection:

OS: I tried both; Manjaro (21.0 with KDE) and Kubuntu 21.04. Both with wayland and X11. Device: HP Envy x360 13 with AMD 4700U APU; with the newest firmware / bios. Dock: HP USB-C Dock G5; with the newest firmware / bios.

Issue: The screens different displaymodes are detected correctly (in system settings as well as xrandr). When activating 144hz, one half of the monitor starts to flicker like crazy and everyhting is kind of moved to the right. So basically very bad artifacts. Also, I have to restart the X session in order to solve these issues.

Please note that I would like to drive the internal (60hz) and external (144hz) monitors simultaneously - is this even possible with X11?

The hardware works as intended with Windows - but I would like to say goodbye to Windows as soon as possible.

Any help is highly appreciated. I will also dedicate time to provide you with more logs / dumps, etc... Just tell me how to get them.

Best

qdrop