What else did you expect from Manchester United? They can’t keep him to be their third choice keeper because it is disrespectful for him because he was the number one keeper for Manchester United, so is better to let him leave to any place that he will have playing time than staying in Manchester United bench for the rest of the season.
Onana should just accept this offer because Manchester United management and Amorim don’t value him anymore, and Manchester United fans are not happy seeing him in their squad because any opportunity they gave him, he always put them into trouble just as he did in the against Grimsby In the Carabao cup as Manchester United get eliminated.
However, he is a good goalkeeper based on history and he can do well in the Turkish league.
Honestly, Manchester United tried for Onana, if he were in a club like Chelsea or Manchester City I believe he would've been sold for long but they still gave him more time to improve and even wasted time in signing a new keeper which was very necessary this summer but that was because they felt either him or Baryindir would improve and in return what did the club get? a shitty performance on his first game this season, that's enough reason to run out of patience and sign a better option. We'll they've made it clear to him that he's neither the first or second choice so if he's wise enough he'll accept offers from any Turkish club that would give him playing time so he can be used as a first choice for his country in the upcoming World cup tournament.