This has been happening for a long time, and I replaced the adapter to a higher Ampere (but same voltage), hoping that was the problem.
I don't think its GPU since when I unplug it from my PC, it still flickers (no video of it).
Is this likely just hardware failure? If I recall correctly, it's about 3-4 years since I bought it.
Video below (careful - it flashes)
Monitor is LG22MK600
flicker.mp4