This SO post from 2018 says it works (and there has been much improvement in WASM land since then, so it is probably even easier now to write a Chrome extension in WASM than it was five years ago). I found the WebNav extension that is open source and uses Rust and TypeScript. It was last updated in November 2022, but I guess it might still be a good place to start looking into building Chrome extensions with Rust+WASM. The Extension-with-WASM repo looks like another great project to look into and see how the basic setup works. It is a very minimal repo, so I'd recommend starting with this. But yeah, you probably have to have at least some JS glue code, though in Extension-with-WASM, it looks very much bearable.