There are some WIP patches in bug 1818502 that implement an http3 server for mochitests under `testing/mozbase/mozserve`. Though not sure why there hasn't been progress in a couple months. Would be good to avoid duplication and either re-use that work or move it over to `wptserve`.
Bug 1818502 Comment 1 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
Edit: Sorry about that!
Edit: Sorry about that, I misunderstood what this revision was actually doing.