To put the question in context, I'll preface by saying that Skip is unique among cross-platform app development solutions in that it isn't imposing an "alien" language or runtime on your app. It uses Swift on iOS, and Kotlin on Android, which are both the first-class recommended development languages for the respective devices. Any translation limitations can always be overcome by branching on the platform/language you are using, and just writing custom code for the platform in question.
That being said, while we have good translation coverage at both the lower levels (Foundation to the Android SDK) and higher levels (SwiftUI to Jetpack Compose), there are many Apple frameworks that we simply don't have any compatibility frameworks for yet. One commonly-request example is maps: we don't have anything that takes the MapKit API and converts into the Google Maps equivalent. However, this doesn't prevent you from implementing it yourself. For a simple example, see the Travel Bookings sample demo at 2:15 at https://skip.tools/tour/skip-showreel/, where you can see how you can drop MapKit and Compose Maps inline into your code.
As time goes on, Skip's community ecosystem of compatibility frameworks will grow and expand. But until then, there aren't any barriers to simply implementing them yourself.
Please feel free to point to a doc that may already answer that.