Two rumors came from Manchester United who are reportedly interested in Tchouameni and also Leon Goretzka. It is unlikely that Tchouameni's transfer will materialize, considering that Real Madrid really protects their players and no other team is allowed to touch him. Meanwhile, Leon Goretzka is likely a pretty good candidate for Manchester United because we know that Bayern Munich are still confused about the transfer of Harry Kane, who has not met a common ground about negotiating an expensive fee.
On the other hand, it looks like Manchester United wants to really tidy up their midfield for the better next season and therefore they still need a good midfielder in order to get the results they want. So far there has been no official offer from Manchester United for these two targeted players.
I don't think Tchouameni would sign for Manchester United now. Real Madrid wouldn't like to let him go just now in the first place. Because why would they? He has been a regular in the starting eleven in so many La Liga games until now. He has a long-term contract (until 2028) also. He is a part of Real Madrid's project now.
Manchester United will need to spend a great deal of money as his market price is €85m also. Rather than him Goretzka is a more realistic target for them now. Because there have been news such as Bayern Munich are willing to sell Goretzka for some time.
His cost might also not be too much for Manchester United which might be around €50m the most.