I have a blue 2024 Crosstrek named Marge (Simpson). I have an iPhone 15 Plus, which has iOS 18 on it, and have been using it through most of the developer releases and it has worked fine, with a few glitches here and there.
I was made aware (from another forum) that there is a CarPlay recall from Subaru available, which you have to go to the dealer to have installed. It is ONLY for people who are having problems with CarPlay. When I was last at the dealer, I requested this update. I was asked if I had problems with CarPlay, to which I replied no. They said they didn't recommend it for people who weren't having problems, only for cars that are having CarPlay issues.
Might be something to ask your dealer about. I believe they told me it was a three hour install. But I could be wrong on that point.
Wish I could be of more help to you.
Mike.