Ubuntu GNOME 20.04, i7 6700, gtx 1660s, recently set to UEFI, 2-3 monitors (2 and a tv across the room for videos), proprietary nvidia driver.
For no reason I can find, my screen freezes for about .1 seconds at roughly 1 second intervals, regularly. It is most noticeable with a mouse, since it makes it really jerky, but exists for video, windows, typing, etc. Audio is smooth, anything non-graphical is smooth, mouse movements are smooth under it but look jerky due to freezing.
Still exists with no windows open, still exists unplugging/disabling other monitors, still exists swapping to noveau. top shows xorg using ~20-30% cpu, system monitor app shows 3-5%. System monitor extension is not installed going by gnome tweaks menu, I've heard of similar issues with it. I've been messing with boot stuff recently (putting ubuntu server on a 1,1 mac pro, which is...hard), but changed nothing I can think of in this install.