With hybrid graphics disabled I have only /sys/class/backlight/nvidia_0 and brightness works correctly. But with hybrid graphics I have both /sys/class/backlight/amdgpu_bl0 and /sys/class/backlight/nvidia_0 . I can offload stuff to Nvidia graphics card and verify it with nvidia-smi but the brightness control is solely on the iGPU i.e in my case iGPU which is a Radeon graphics. This is known as Nvidia PRIME IIRC.