All three use federated groups: https://socialhub.activitypub.rocks/t/groups-implementation/591 https://socialhub.activitypub.rocks/t/groups-implementation/...

All three use federated groups: https://socialhub.activitypub.rocks/t/groups-implementation/591 https://socialhub.activitypub.rocks/t/groups-implementation/... There are groups on Mastodon that you can join and follow.