I recently installed Ubuntu 20.04 on a new Dell Vostro and I'm facing a screen brightness issue. It seems that the brightness is adjusted based on the current window. If it's brighter, the rest of the screen (like the bottom bar) gets darker, and the other way around. Consequently, it is most apparent when selecting a text in terminal or in Intellij Idea (selecting text makes the background go darker).
See it in action here: https://makeagif.com/gif/ubuntu-brightness-afO1vb
For some reason it's way less visible here than in real life, but you should get an idea about the issue. I tried a bunch of things, but none of them worked. Any ideas?