Comment 27 for bug 1995320

A couple more data points.

I installed and booted a 5.19.17 mainline kernel (from the ubuntu mainline kernel archive) and the static started immediately.
I booted the 5.15.0-52-generic kernel left over from ubuntu 20.04 and haven't had any problems with static or full screen video after 30 minutes.

This seems to point toward a kernel/driver issue rather than gnome-shell.