"Help us; send beer" it said on the students' post-it notes. Hardly contraversial.
If a large secondary school, like ours, can manage to contact-trace & isolate small numbers of students & staff, then surely a university hall can manage it?
You zone your hall up by floor/ corridors & ask those who can wear masks to wear them in communal areas (seeing as that is how everything else is being done). If the students mix outside of the hall then well, that is what school kids & workers do, they leave their homes to go to school & work, & get shopping, & sometimes go out elsewhere.
If one of them tests positive you only ask the people living in their zone/ close contacts to self-isolate. No need to keep them all in.
I suspect that thanks to the general grumbling that students spread disease, the universities are keen to be seen to be doing something to placate local communities. (Forgetting how much financially students contribute to those communities)
As for Christmas, that's too far off for me to consider. I can imagine that if we are allowed to mix households we will then be all told off & subject to strict restrictions in January. But as I say, it's too far off to think about. Seeing as how pretty much everything I've planned this year has been cancelled...