Display Flickering Issue

[MrPhantastic]

Hi people
I'm having an issue with my screen (I think lol).

Let's start with basics:

R5 3600
16gb 3600mhz
Rtx 2060s
ASRock x570 mini itx tb3

Monitor I'm having issues with: LG 29UM57-P

This problem only occurs when I am playing games, and when not in windowed mode (so I'm having this issue in fullscreen and borderless). I've never seen the problem occur while playing YouTube or in full screen VLC.

The issue is that every few 10 or 15 seconds, the screen randomly flickers for a split second. Sometimes it occurs on the bottom third of the screen, or sometimes the whole screen flickers.

I know its:
- Not the graphics card (I switched it out with another 2060s, same problem.
- Not the drivers (I did a full install and reinstall)
- Not a specific game (having problems with all of mine - beam.ng drive, Far Cry 5, Snowrunner)
- Not cables or ports (I switched both, and I know they work fine with another computer)

I did some testing on another monitor, and it works fine. I know someone's gonna get mad that I basically posted something that is already solved, but I'd just like some agreement that it's a monitor that's suddenly gone wonky - before I buy a new one. Are there any other possible points of failure that might be causing this issue? Thanks for all your help.