The next challenge is finding good, actively maintained WebAssembly binary blobs for all of the languages I care about.

Pyodide provides one that works well for Python.

I'm finding it surprisingly hard to find a good option for JavaScript. QuickJS or one of its forks might work but I've not yet figured out the incantations necessary to do that.

Then there's Lua, Ruby, PHP, etc - ideally I'd like there to be robust, well maintained, well documented WebAssembly versions of any language that I might want to run code from.