> even during the window of opportunity with Scala on Android.

I don't understand this. You can run any pure Java jar on Android, pretty sure you can do that with Scala too? It's not exactly a "different platform" in terms of programming language. Sure it needs tooling and specific libraries, but that's higher level than the programming language.

Jetbrains is doing interop with Swift (Kotlin -> ObjC -> Swift and more recently Kotlin -> C -> Swift), which Scala never did. But I don't really see how this is relevant in this conversation.