Why would you need to control these through a mailing list? The maintainers should have accounts (I don't see the point in federating maintainers instead of just discussion, especially when this is self-hostable), and only those with permissions should be setting up labels, assignees, inline reviews, and CI. And yes, sourcehut has a UI for this, though alternatives through email commands are also available.

And no, I do not see the point of reactions. If you really need a vote, use a voting service.