@interledger @evan If anyone would like this bounty, then you can fork @peertube/http-signature into its own NPM namespace using my forked branch, which provides a backward-compatible RFC 9421 implementation that would make it easier for software to handle both cavage-12 draft and RFC 9421. You will probably need to maintain it for a couple of years so that the JavaScript/TypeScript ActivityPub community can coalesce and focus on a stable replacement (probably fedify or misskey).