A difficult period may be beginning for Real Madrid. In this case, Ancelotti will have a big job. Ancelotti must manage Mbappe's ego well. If this will cause unrest within the team, they may even leave him on the bench. No one can be the main player of the team. This situation varies depending on the environment you are in. I see Mbappe's joining the team as positive, but they have to overcome these problems as well.
On the contrary, Ancelotti job will become easier and it will not be too difficult to control Mbappe. It's different when Mbappe was at PSG and now at Madrid. It is clear that Madrid is not the type of player who is filled with ego, at PSG you should know that since there are Messi and Neymar and then Mbappe, 3 ego players will be increasingly difficult to control. But Madrid has Vini, Rodrygo, Bellingham, all of whom while at Madrid did not show selfishness. Honestly it's all just a worry for rival fans who think that Mbappe will be difficult to control but in reality it's easy for Ancelotti. Believe me in Madrid you will feel a harmonious squad.
if Mbappe is really egotistical, we still have quite a long time before the season starts. With enough time everything will be under control. Mbappe first appearance will be against Atalanta in the Super Cup and in time Mbappe has fully adapted.
The only thing Mbappe is probably thinking about right now is the European championship. They will play successful matches for France in this tournament. I'm sure of this because France is one of the strongest championship candidates of the tournament. Ancelotti will also follow this closely, because monitoring Mbappe and integrating him into the team more accurately should be the most important thing he thinks about right now. If Mbappe behaves without ego, it will make Ancelotti's job much easier, but if he behaves with ego, then Ancelotti will try to maintain balance.