At the beginning of Sancho move to Manchester United, Sancho was able to show a pretty good and impressive performance, but his dispute with ten hag actually made him removed from the main squad, ten hag big ego made him not care to back Sancho even though Sancho at that time performed quite well, Ten Hag ego made the dispute even bigger and made Sancho want to leave Old Trafford at that time, Dortmund managed to get Sancho as a loan player without waiting long Sancho was able to show his great form this season again and help Dortmund reach the Champions League final.
Sancho still has a contract with Manchester United and reportedly Manchester United will not release Sancho at a cheap price to Dortmund, besides that Sancho reportedly wants to return to the Premier League and play for Manchester United on the condition that Manchester United must fire Ten Hag from the coach, if not, otherwise Sancho prefers to be sold or loaned to another club, Sancho and Ten Hag do not seem to want to give in to their dispute so indeed Manchester United is currently in a considerable dilemma between choosing Ten Hag or Sancho.
not only Ten Hag, but Sancho as a player also feels that he is innocent and has a big ego, which means that neither party will give in for the sake of the team, so one of them has to give in to leave Man United.
I won't side with anyone but it's a shame that a big team like Man United has to have problems like this which makes the team's reputation decline a little more and certainly has a bad impact on the team's performance which has to lose a talented player like Sancho and there should be the best solution for this reconcile the two parties between Ten Hag and Sancho but it seems difficult to reconcile these two parties.
one of the best solutions for Man United might be to choose to keep Ten Hag and sell Sancho to another team as you have said.
one of Sancho selfishness as you have explained is proof that there is no other way than to offer the player to another team and Dortmund to take the opportunity to get Sancho but if Man United gives a high price it will actually have another bad impact when Dortmund refuses to pay bigger and in the end Sancho will only be a reserve player.
but don't worry because even though the offer given to Dortmund will be very expensive, there are other teams who will definitely be eyeing this player, such as Chelsea, who may be able to pay a high price.