12.1 introduced the issue(s) for me. USB-C connected hubs, video via USB-C (i.e, my external monitor), are unrecognised now — they were working without any issue before the update, under 12.0.1. The monitor is a Dell U3219Q. HDMI video now randomly flickers off and on often enough to be unusable. DisplayPort via a 3rd party adapter works, but a third party USB hub doesn't.