Beware of the following: many English clubs make mistakes (Man U, Chelsea, Tottenham) when it comes to picking a manager - this has to do with the rather closed football culture England has, where they judge what's going on in mainland Europe through English eyes; that is, based on results and statistics and not so much the characteristics of a person, whether a person would fit into the culture, the job, the club.
The cultural aspect is being vastly underestimated: not many football coaches from mainland Europe have it in them to adapt to England as a (very closed) football culture, the job of a manager (instead of a coach) and the characteristics of a specific club (mismatch: some people just don't fit at certain clubs).
Erik ten Hag is a very good example. Great coach, great football crazy guy - but a manager? And just because he previously had excellent results at Eagles, Utrecht and Ajax, does not mean you're suitable for a managerial job in the English Premier League. The results might say yes, but he was head coach in the Netherlands, not manager of an England based football corporation. And he was excellent in the Dutch system, where we're used to sell off our stand out players and instead integrate up and coming youngsters. Quite different from what is expected of you at Man United, where you need to lead a squad of mostly well established stars.
Anyway, about your options. Again, I look if a person would fit in the country, in the job, at that club...:
- Diego Sieone is stuck at Atlético Madrid and I don't see him move outside the Latin spheres (Southern Europe, South America)
- Hansi Flick is another character of whom I think won't make it outside his beloved native area.
- Ruben Amorim is an interesting one - for him, Man United would be another step up the ladder. His 3-4-3 is attractive and attacking. Good one
- Graham Potter is overrated I believe. He had a good run at BHA but if you put it next to what is successor De Zerbi is able to do, Potter's achievements were modest at best and his results at Swansea or Chelsea weren't that great either. His great plus however, is that he does know what it takes to be a manager in the English sense of the word.
So, I'd narrow it down to Amorim and/or Potter.
And then, Ratcliffe needs a good PR-/Communication director to get across that it will be (another) transition period for Man United first. The position as Communication Director is something where you could put yourself into the story.