i am experiencing this as well. there are people have been experiecing this for months on big sur beta, just read on reddit. how on earth was this allowed to be released like this with it occurring for months in beta? my hp running windows detects the external monitors i am running, just fine. without zero issue. not a cable or a monitor issue. i had recently upgraded to big sur and now this is occuring. was not occurring previously. this is a big sur issue 100% and it has been going on for months now

I too am experiencing this issue. it's not a monitor or a cable problem, already checked with hp running windows this has been occurring for months now, i've read posts about it on reddit from months ago during beta this is a Big Sur 100% issue

I have the same issue with usb-c alone, this has been occuring for months now on Big Sur. There are reddit posts about it from months ago. it's a big sur issue, and how it was released like this is beyond me. already tested the monitors using hp running windows and they work fine. i just upgraded like a week ago and now they monitors are not being detected. both of them.