It would be wise for Manchester United to look for another goalkeeper besides Onana, who has frequently made blunders for the team. Moreover, Onana has had a history of injuries like this, so the team needs to have alternative goalkeepers so that Manchester United can be in good shape when the season resumes. I also want to see Manchester United undergo changes for the better next season, so every player must be healthy, and the team must also be willing to buy new players to strengthen the team even further compared to last season.
There is a simple maths we need to know about Manchester United and some players. You see Onana and some players that are too good with honest mistakes, it's because they had a long term contract with the players and they are most likely paid average wages but the sign contract on their release clause were higher. Now, it's not about signing or replacing the players but which club is going to buy those players at expensive price even if they want a small pay.
Manchester United doesn't want to accept any release clause close to their plans and it obvious that most of those interested club want only small or fair amount that the player is worth. Even if I'm not a financial coach or manager, I will not want to sign huge amount of money on Onana, it will be a waste of money so that's why you see some players are stuck with Manchester United and no club want to buy any player that are not doing and yet over expensive.