He could stay with Germany if the Euros go reasonably well, he seems to be Bayern's first choice and he's of interest to Liverpool. It's probable he would turn down the United job given the alternative options he has but I would hope that the club were at least seeing if it's possible.
My guess is that Liverpool are hiring Amorim as the media coverage I read makes me think they have been preparing people for it with leaks already.
Nagelsmann no idea. His record was better than Tuchel's and I now assume Xabi Alonso wants to coach Madrid instead, so maybe they bring back Nagelsmann. No idea what their alternative is. Betting suggests De Zerbi is the favorite.
We might end up just getting whichever of De Zerbi or Nagelsmann prefers us or Bayern doesn't choose.
I guess they're my first 2 choices, though I'm no Nagelsmann expert. Bayern firing him was odd enough that you wonder if there wasn't some serious reason as to why it occurred, but he then got the Germany job so who knows. Firing Neuer's goalkeeping coach and alienating him seems like a weird move to make, so maybe he's power-mad or something, but a young highly rated coach like him who did fine at the one job he got fired from might be our best chance at getting an elite manager, for which we have to be lucky and/or clever without a 2015 Pep or Klopp on the market who wants to come here.
I've always been fine with us hiring someone like De Zerbi because I think even if it fails it probably sets you up better for the future to be playing good football (move on from McTominay and Wan-Bissaka athletes who can't play pass and move football and older players and keep the club from being interested in those sorts of buys), and I think we're at least 3 years away from challenging for the title even if we rebuild the squad correctly barring a miracle or a manager just transforming us, and an ideologue and highly rated tactics guy like De Zerbi is probably more likely to do the latter.