I tried looking for the webasm version of ECL, but couldn't find it. The official ECL homepage doesn't mention a wasm target. Do you have a link maybe?
For context "jackdaniel" is Daniel Kochmański, ECL's maintainer, so 4 months ago at least it was planned to be merged for the next release.
Branch is at https://gitlab.com/embeddable-common-lisp/ecl/-/tree/emscrip...
I suspect the work is still ongoing. But maybe not on priority.
This diff from around 3 months ago shows it's likely possible to run it in the browser currently but with a lot of caveats (pretty great nonetheless!).
https://gitlab.com/embeddable-common-lisp/ecl/-/commit/6af4b...