I don't believe the rumors of a rift or a bad relationship between Mbappé and Vinicius, as the media has been constantly highlighting these issues since Mbappé's arrival at Real Madrid, but they're not.
Mbappé and Vinicius are two key players in Real Madrid's attack. This is just a rumor, and I'm confident they'll both stay at Real Madrid. Xabi Alonso is also a brilliant and authoritative coach; he'll surely be able to unite these two players to improve the team.
I, on the other hand, had heard the same things, even two months after Mbappe's arrival, i had heard that he was a pain in the ass and a troublemaker and that he was ruining the dressing room.
I don't really know how much of it there is, but if so, it's not a good thing. For the team, but also for the player.