The screen becomes darker whenever the fps drops to 60
The colors on the screen very visibly become darker about a second after going in or out of anything when using the automatic refresh rate option, it could be when I'm going between apps, opening a new page or even when pulling down the notification panel, it happens all the time.
Video example: https://imgur.com/a/zVJPYyL
Now I think I found the source of the issue.
Enabling the "low brightness DC dimming" option in the display setting, which is only allowed when the phone is on 60fps, solves the issue completely by simply always being darker, but then again, you must force it to be on 60 fps.
So I tried going back to the automatic refresh rate, but now I monitored the fps, and the issue became very clear.
Whenever the fps drops to 60 the DC dimming is probably enabled automatically, even when disabled manually on the settings, causing the screen to become darker whenever it switches between 60 and other refresh rates, since this feature is not supported on higher ones.
Video example: https://imgur.com/a/JK9tAtR
Look at the color of the keyboard and notification panel when the fps switches from 90 to 60 and vice versa, note that it is more visible than it looks on the video