I see, still a really cool project! Is accessing the internals simply not possible or just really hard to pull off programmatically? I am wondering about that because I never found anything in the android space to enable that without resorting to Kotlin/Java components.

You can call into to the JVM via FFI (e.g. using the jni crate in Rust), but it's not very nice. And most of the abstractions people have written thus far seem to be primarily (or solely) targeting the "Java calls into native code" use case rather than the "native code calls into Java" use case.

I'd love to see something better here. I suspect it's possible.

It's limited to what NativeActivity / GameActivity can provide. And as @nicoburns mentioned, you'll have to use FFI if you want to access some Android functionality. But it doesn't always go smooth. For example, all my attempts to fix issues with software keyboard didn't work.