S3220DGF, AMD FreeSync on, brightness changes/flickering, #2

Man, I have the same issue, same monitor, same firmware. And I have the Nvidia GTX 1080 Ti. All the reviews online from reputable reviewers says that it works fine with G-Sync, it doesn't. Same flickering issue. It's so distracting and annoying. I bought new DP cable, tried few of them, different setting, driver versions everything to no avail. But I thought, okay its AMD Freesync, its not meant to be used with G-Sync, so i bought an AMD 5700 XT video card, reinstalled windows, all latest drivers and everything, and you guess what? Same issue. I really wonder how is this possible. Then Iv'e decided its the monitor. Called Dell support, and after some investigation they have sent me a new one. Same firmware though, but a brand new unit. Well, you guessed it right - same issue. Now I end up with a spare video card I don't need, a monitor which a bought exclusively for AMD Freesync, which I cant use.

System:
MSI x570 Gaming Plus
AMD Ryzen 3700X
32GB. DDR4 3200MHz Corsair Vengeance Pro
Windows 10 Pro