I was facing a very annoying screen flashing/flickering of backlight with Ubuntu 20.04 LTS on Dell XPS laptop. After some searching I found this thread with a user reporting similar issue:
Then I edited the grub config file:
$ sudo vi /etc/default/grub
Changing the default parameter to:
GRUB_CMDLINE_LINUX_DEFAULT="i915.enable_psr=0 quiet splash"
$ sudo update-grub
It didn’t fix the issue completely, but now it is at least more smooth and don’t bother me too much.
Update: Changing the Power settings Automatic Brightness to Off and Dim Screen When Inactive to Off solved the remaining issues.