Update 11th October 2022: Both Ubuntu 20.04.5-LTS with HWE stack, and the current Ubuntu 22.04.1-LTS now have the bug-fixed kernels available as part of their regular software updates. Specifically Ubuntu kernel versions “Ubuntu-5.15.0-50.56” and later are now fixed. So simply triggering a regular software update and a reboot of the machine will fix this problem on AMD Polaris and Vega graphics cards, making devices from VPixx or CRS work fine again.
→ Case closed, with a total time from diagnosis to easy to install bug fix of 3 months.
-mario