Took me a time but here are further results:
It doesn’t matter if I first power on the laptop and then connect the dock with power, or without power and then plug in the power into the dock.
The result is always the same: Laggy System with 100% CPU utilization
Furthermore I tried a fresh Ubuntu 24.04 and Debian 12 with gnome and Windows 11.
Always the same thing. As soon as the dock gets powered, the cpu utilization spikes.
A interesting behaviour in Windows 11 is, sometimes the CPU doesn’t spike to 100%, but just freezes for like one or two seconds, then it’s slow for about 5 seconds and freezes again.
The event viewer in Win11 does only show a Event 105 (Kernel Power)