I've installed ubuntu 20.04 and during installation because of issues I was facing related to acpi error I've resolved it by adding "nomodeset" after quick splash in command line. but now I'm unable to change brightness...I' ve tried all possible methods mentioned here: Ubuntu 20.04 brightness adjust not working, https://stackoverflow.com/questions/11523523/how-can-i-change-the-screen-brightness-of-my-laptop-in-ubuntu but still not been able to resolve this issue.
System info: Cpu: Amd radeon 4500u Gpu: integrated graphics
nomodesethas nothing to do with ACPI. And understanding what the parameter does - it overrides any graphics drivers and sets a generic VESA video mode - should easy to understand why driver specific functions do NOT work. I suggest you remove it. AMD graphics should work out of the box with already installed open-source drivers. No user action required. – ChanganAuto Nov 18 '21 at 13:30