In addition to Milan, I have heard of some other European teams also being after Akanji recently.
Actually Galatasaray has already been in talks for him. They have reached an agreement with Manchester City too but still no green light on the player side...
I wonder, what is taking him so long?

He isn't a starter at his team anymore and not much time left for the end of the transfer window for European leagues.
It seems Akanji is not keen on moving to Turkey since he's not even discussing personal terms with Galatasaray. If he does not leave this summer, he won't get enough minutes at City because Pep Guardiola does not regard him as an important member of his squad and it might cost him his place in the World Cup. Whatever his decision is, he should think very carefully.