[mhfu]

Don't know anything about Scala. Kotlin has null safety and a bit cleaner syntax, but other than that, I don't see too much advantage over Java for backend. In Android, Java is still lagging behind a lot. Also, Jetpack Compose, a declarative UI framework is Kotlin only. Kotlin is also working on wasm (so is Java I think, but Kotlin has working examples with wasm GC) and Jetpack Compose is going multiplatform, including wasm. This video has some examples in description https://youtu.be/oIbX7nrSTPQ

[kaba0]

There is teavm and cheerpj which can already execute java (or any jvm class file) in js or wasm.