Add to boot optins to control bightness. For disable control for amd gpu
kernelstub -a amdgpu.backlight=0
Nvidia driver bug with backlight. You may install 460 driver, but it doesn't work with new kernel 5.13+(?) https://forums.developer.nvidia.com/t/laptop-backlight-control-regression-with-465-24-02/175585/48 Temporary solution for backlight
xrandr --output DP-4 --brightness 0.5