Still hasseling with this problem.... I am now believing, that the reason of the problem is either a BIOS issue or a kernel issue.
Tested several things and I the issue appears as soon as the kernel is started. In the internet I found informations, that if the BIOS does not see Windows, it may disable several functions. Here a kernel parameter like acpi_osi=Linux or similar should help. Tried several combonations, lie acpi_osi=Linux or acpi_osi=!Windows 2022 or acpi_backlight=vendor and combinations of this - but got no success. However, it is clear, the functions like screen brightness etc. stop working, as soon as the kernel loads. When grub is active (active here means: boot grub menu, where to chose the kernel to start), the brightness of the screen can be changed. But as soon I press enter, and the kernel loads, it stops working. At that moment /usr amd /var are still not mounted (as I have to open the encrypotion manually). This means: No configuration is involved and no other binaries. Thus let me conclude: It is a kernel issue with the BIOS and the only way I see, will be to enter some parameters like described above. However, though reading a lot of manuals, I am lost, what to set and how to start. And in the internet I saw many many people as lost at me with the same issue. I have the hope, some kernel developer might read here or some specialist or someone got into the same issue than me. I will work on and try harder, but at the moment I am stuck. Thanks for reading this. Best Hans
