To add more info on what I tried, I have put it here: https://askubuntu.com/questions/1329928/legion-5-pro-brightness-control-doesnt-work-on-ubuntu-20-04-with-nvidia-driver . Surprisingly the brightness also works on Manjaro (as mentioned in my post) after adding 'Option "RegistryDwords" "EnableBrightnessControl=1"' to x.conf.d. Also, it also works on Regolith Linux 1.5.3.
To add more info on what I tried, I have put it here: https:/ /askubuntu. com/questions/ 1329928/ legion- 5-pro-brightnes s-control- doesnt- work-on- ubuntu- 20-04-with- nvidia- driver . Surprisingly the brightness also works on Manjaro (as mentioned in my post) after adding 'Option "RegistryDwords" "EnableBrightne ssControl= 1"' to x.conf.d. Also, it also works on Regolith Linux 1.5.3.