I think you meant Java and now Kotlin? Google never recommended Dart for Android development. They have Flutter which uses Dart, but that positions itself as a cross-platform way to build apps and doesn't have any support from Android tooling or things like that. It also still positions itself as an alpha, so do with what what you will.
But Kotlin also works just fine on JVM. So Kotlin works on MacOS, Windows, Linux, and now Android. That sounds pretty cross platform to me. Kotlin is also not a language from Google, so I don't know why you're annoyed with Google on this one. Kotlin is from JetBrains.
I think you meant Java and now Kotlin? Google never recommended Dart for Android development. They have Flutter which uses Dart, but that positions itself as a cross-platform way to build apps and doesn't have any support from Android tooling or things like that. It also still positions itself as an alpha, so do with what what you will.
But Kotlin also works just fine on JVM. So Kotlin works on MacOS, Windows, Linux, and now Android. That sounds pretty cross platform to me. Kotlin is also not a language from Google, so I don't know why you're annoyed with Google on this one. Kotlin is from JetBrains.