The type system introduced in Wasm GC allows sharing data between the host and other modules and is usable right now. DOM access is possible and being demonstrated in several language implementations.
Edit: is this it? https://www.spritely.institute/news/building-interactive-web...
Edit again: apparently I had seen this before, since I upvoted its HN submission. Oops! https://news.ycombinator.com/item?id=38477602
TypeError: WebAssembly objects are opaque
When trying to read/write WASM-GC objects in JS.