Having a similar issue MBP 16" 2020 - part of the screen becomes black and green with minor flickering I was hoping this would get fixed by Big Sur 11.1 but I updated and I am still facing the same issue. Note the screen flickering doesn't happen instantly - it seems to take a few hours before it starts - and it also seems to be monitor agnostic because I see the same issue on my macbook screen and on my monitor.