Mailing lists are terrible. That's part of why source forges became a thing. You can send pretty much anything into mailinglist in any format you like.

Exactly this. IMO we just need better ways of rendering a mailing list inbox as a series of issues/PRs. And maybe better tooling from IDEs to "open a PR" using git send-email.

Source hut is close to my ideal here, but still seems rather complex. Maybe I just don't appreciate the necessary problems it solves yet.