If you want a sing song, then clearly it’s the Bishop’s Blaize. No, I haven’t been in myself on a United match day obviously!
However, if you’re prepared to sacrifice some of the atmosphere, a decent place for a drink where you can get served easily and hasn’t been mentioned so far is The Dockyard at Media City. Conveniently located adjacent to the Media City tram stop, I’ve been in there prior to most recent Old Trafford derbies - it’s a pretty safe haven for us blues even though plenty of United fans use it. Loads of decent beers on tap which are served in glass pint pots rather than plastic glasses, and a 10-15 minute walk to the stadium.