None of them went from a Brighton level team to Manchester United level though except for Conte basically. They all made gradual progression steps or managed the 2nd club of the club itself/while also playing for that club then managing it later on.
Klopp went from Mainz to Dortmund. A step up, but not comparable to the step up Potter would have to take. Tuchel was the same.
Enrique and Pep both managed Barcelona B. Enrique even managed Roma beforehand.
Nagelsmann going from Leipzig to Bayern isn't comparable to going from Brighton to Manchester United.
Zidane managed Real Madrid Castilla.
None of those examples are comparable to Potter. The only one is Conte going from Sienna to Juventus.
And again, I'm a fan of Potter too. I just don't know how he'd handle the pressure here. That's a massive step-up.
I'd disagree about Klop. When Klopp went to Dortmund, Mainz were a barely promoted team. Dortmund are the second biggest team in German football. It's a pretty big step up even if Dortmund were on the down (so are we right now).
Barca B is equivalent to a championship side, even worse. They definitely did not have the experience of coaching Barcelona who were having a bad season but previously were coming from one of their best seasons and had stars like Ronaldinho in. Guardiola definitely did some great things in Barca B, but he had miniscule experience, let's be honest.
Why not? Leipzig, as good as they were, are a newly promoted side in German football. They are definitely nowhere near Bayern in terms of stature. Why is it not a big jump?
Real Madrid Castilla are equivalent to a championship side, same as Barcelona B.
Potter also fits your criteria, his success in Norway in European competitions is evident. His success in England with Brighton, especially against big teams, is evident. If we go by who is ready made to take the helm at United, well, you can probably count them on your one hand - Conte, Klopp, Pep. That's it. You'll always find some fault in the rest. To me winner coaches and loser coaches are easy to spot. You have coaches of the mold of Pullis, Big Sam, Moyes who are good at their level but do not have the mentality or tactical nuance to coach a big club and you have coaches like Potter, Ten Hag, Nagelsmann who are more often than not a huge success wherever they go. They often have a clear vision on how their team has to play, they are winners in terms of mentality and they are very passionate about football. In others words, the antithesis of Ole as a manager.