https://bugzilla.kernel.org/show_bug.cgi?id=203905
--- Comment #30 from Paulo Nascimento (paulo.ulusu@googlemail.com) --- laptop: Lenovo Legion 5, amd ryzen 5 4600h Graphics: Device-1: NVIDIA TU116M [GeForce GTX 1660 Ti Mobile] driver: nouveau Device-2: Advanced Micro Devices [AMD/ATI] Renoir driver: amdgpu Kernel: 5.12.0-1-MANJARO x86_64
I have loaded kernel 5.12 and enabled the patch with amdgpu.backlight=0. The brightness controls Fn+F5/F6 works as well as the controls in KDE panel.
There are still the error messages at boot and shutdown though.