Guppe groups look like regular users you can interact with using your existing account on any ActivityPub service, but they automatically share anything you send them with all of their followers.
Follow a group on @a.gup.pe to join that group
Mention a group on @a.gup.pe to share a post with everyone in the group
New groups are created on demand, just search for or mention @YourGroupNameHere@a.gup.pe and it will show up
Visit a @a.gup.pe group profile to see the group history
is this like a hashtag?