For Apple phones there is also the recently published Every Door app: https://every-door.app/

It'a however a little bit more technical and not all gamified and glossy.

I am always amazed at the effort in UX that StreetComplete has taken. Which sadly is also a reason why rewriting it in something that runs on iOS is a major undertaking. And replacing all those beautifully-designed quest screens with simple key-value pair tables is obviously not a suitable replacement.