Ill tell you'll something, i haven't tried yet but get the new latest hdmi or display port like 4k ones and then try if the problem exists or not. Even I upgraded my pc my gpu from asrock rx580 to rx 6600 XT, now only 2 things are remaining which are cpu and motherboard. If that new cable doesn't fix it then it could be motherboard (though chances are slim for the motherboard to be the culprit). If nothing then it's monitor problem, i first thought it could be the wire that supply power to monitor must be causing this, try changing the cables that's what I'm thinking to do now
