This is Thinkpad T480s with 8th gen Intel graphics and 1440p screen (doesn't happen on 1080p screen, I suppose won't happen with discrete graphics, but I have nothing to test with). This only happens on Xorg, not on Wayland (however there are still minor graphical glitches there are well). All firmwares updated, using recent kernel with decently sane config. I have two laptops with exactly the same hardware, and it happens on both. What is this?