nvidia.NVreg_RegistryDwords=EnableBrightnessControl=1 works for me!
The /etc/default/grub file.
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nvidia.NVreg_RegistryDwords=EnableBrightnessControl=1"
sudo update-grub
But I have set ‘Discrete graphic’ in BIOS Settings. I haven’t other changes of a clear system, only grub and BIOS.
Without this configuration it didn’t work for me. Also I had limited settings for NVIDIA settings when I had Security Boot Enable. When I had Security Boot - Disabled I had more settings, but I hadn’t display configuration.
When I have updated BIOS settings and Grub I have got worked brightness.
My laptop is Lenovo Legion 5 Gen 6 (NVIDIA + Intel graphics):
- NVIDIA Corporation GA107BM [GeForce RTX 3050 Ti Mobile]
- 11th Gen Intel(R) Core™ i7-11800H
NVIDIA driver 470.82.00 from Ubuntu Additional drivers.