Hello, have you tried this? https://iristech.co/how-to-test-my-lcd-monitor-for-subpixel-flicker/
It doesnt show any flicker on waterfox on my trusted laptop. On new firefox that is painful it shows banding on 2a,b and 4a,b.
martin That's LCD inversion flicker it's testing for I think. more info here
One thing to keep in mind is that the info at that link is old, doesn't cover PWM, etc.