An off-field scheme could be between Galatasaray and Copenhagen who are trying to keep Man United out of the Champions League. This of course does not rule out the possibility considering that Man United facing Bayern Munich is a serious obstacle. Playing at Old Trafford is not a big problem for the Bayern Munich team because the Red Devils are no longer scary to face. I agree actually in Group A Man United is still said to be safe but as safe as it is Man United still can't prove that their game is promising. It's a shame that the front line has been solid in building attacks but Onana has again put himself in a position that United fans don't like. There was a lot of speculation blaming Onana for the draw well when the front line struggled desperately to score 3 goals it ended with sharing points which didn't benefit Man United at all.
Galatasaray and Copenhagen both want to win because they both have the same chance of qualifying from the group phase, while Manchester United must win against Bayern and have to wait for the results of the matches from Galatasaray and Copenhagen.
So I think everything is possible here and Manchester United still has a chance to qualify even though the percentage is quite small.