are you asking if kotlin native supports wasm?

I know that theoretically it does, I was wondering how much experimental it was and how much can be done in practice

You can compile pure Kotlin programs, with some JS APIs bindings, one serious limitation is lack if runtime exception support (due to WASM limitations).

Kotlin Native DOES work in wasm (in practise with the sample via the CLI - https://github.com/JetBrains/kotlin-native/tree/master/samples/html5Canvas ). One of the main limitations is that there is no system for web/JS API interop. This will prevent some Kotlin JS libraries from being ported over to Kotlin Native.