The Android Open Source Project is awesome. It's not hard to compile it yourself and run it on a pixel 9. The issue is the hardware imo. (And some of the apps in AOSP really suck, but the actual OS is great imo)
Unless you're using a language that's specifically compile-to-jvm (e.g. Java, Kotlin or similar), almost nobody is using those JVM alternative runtimes. They're usually second-class runtimes that don't run the entire ecosystem of the target langauge. React Native runs JavaScript in a separate JS VM, Flutter is compiling Dart to native code with emdedded runtime, and Rust UI code also compiles to a native binary.
The "lingua franca" for language bindings is the C ABI which every other OS's platform libraries (Win32/Cocoa/GTK) support.
> The "lingua franca" for language bindings is the C ABI which every other OS's platform libraries (Win32/Cocoa/GTK) support.
Which is more like half of an API, it doesn't specify lifetimes so basically anything behind a pointer is unusable in itself. That's why we have "hacks" like gobjects and such, and why using most of the bindings is only possible if you have a decent binding library.
And in particular, people might lurk for a long time without an account until one day a thread makes them want to comment so much that they go ahead and create an account to comment.
Although, the username they picked in this case does seem a bit specific to the topic of the single comment they wrote. So it remains to be seen if this particular case was a throwaway account only used once, or if they will keep it.
Also usernames/handles can be surprisingly hard. It seems reasonable to me that people would pick something related to what they are thinking about at the time.