Wasmtime implements a remote debugging server, so that you can debug guest programs with a recent build of LLDB. Set breakpoints based on the source language symbols, single-step through wasm opcodes, anything you'd expect: https://docs.wasmtime.dev/examples-debugging-guest.html
still useless. I had an idea to offload parts of my game core into wasm leaving only UI in the browser - I abandoned that idea when there was absolutely zero possibility for me to debug in browser what is wrong with my core. i just rewrote everything to TS (from rust)