I have the same issue on a M1 Mac Mini on Big Sur and it seems to occur while using Chrome. Scrolling through Facebook feed seems to trigger it often, also autoplay videos on some news sites (like CNN). Surely there has to be a way to prevent this, I would even accept the operating system causing the program to crash right before this happens. But it's unacceptable that the whole screen continuously flickers (causing who knows what harm to my monitor until it stabilizes again.) I won't blame Google (even though there may be some bad programming lines in Chrome), the operating system should not let the program harm our equipment in this manner. I just switched over from Windows and hoping very much not to switch back as apart from this MAJOR issue, I've been quite happy being a MAC user.