As I said before, there are rumors about Arda Güler, and yet this is not confirmed by anyone anymore. All we know is that Mourinho wants to hire this player for Fenerbahçe after the other team in this league hired Osimhen. Now Fenerbahçe doesn't want to lose the race, and they also want to improve the teams.
When Güler joined Real Madrid, he couldn't perform well in the first days because of injury, but he improved over time. Now, I don't think Real Madrid wants to lose this player, considering his age and talent. Maybe they will just get Güler on loan.
Andriy Lunin, signed in Jul 2018, never played, Real Madrid loaned him to Leganes. After that Real Madrid choose to loaned him to Real Valladoid and then Real Oviedo. Now, as we can see Lunin becomes second goalkeeper.
Valverde, signed in Jul 2016, but he played for Castilla and in the next year Real Madrid loaned him to Deportivo La Coruna. Now, as we can see he become one of the best midfielder that always become starter.
I don't see anything wrong if Guler loaned to other teams as a stepping stone.