The amdgpu.backlight module option was already merged in the upstream, so TW should have a workaround (passing amdgpu.backlight=0 boot option). This was also already merged in SLE15-SP3 / Leap 15.3 kernel, too. But I don't think we'd fix this for Leap 15.2. The root cause of the problem hasn't been figured out yet. My bet is that it's a BIOS bug, and more proper workarounds are needed in AMDGPU driver side, but this has to be sorted out in the upstream development. Feel free to join to the upstream gitlab Issues.