It is now possible to build and upload PyEmscripten wheels through pyodide-build or cibuildwheel and upload to PyPI. The uploaded wheels can be installed and used in any platform that satisfies PyEmscripten, including Pyodide.
We recently published a PyEmscripten wheel for pydantic-core (the Rust core package powering Pydantic validation and serialization), available with Pydantic v2.14.0a1.
To raise awareness, I wrote a blogpost/guide on how to setup CI for Rust based projects using maturin. The process is a bit convoluted, but hopefully we will be able to simplify it in the future.