piefed

PieFed just added a multi-reddit feature, which we're calling "Feeds". It combines multiple Communities (actors of type "Group" in ActivityPub) into one.

Feeds can be followed from other PieFed instances, which will subscribe the follower to all the communities in the feed.

Try it out at https://piefed.social/feeds

It's similar to PieFed's concept of a Topic https://piefed.social/topics, except topics are maintained by the instance admins. Feeds are crowdsourced and federated topics.

When you subscribe to the feed (which you can do from a remote Piefed instance, you don't need to be on the same instance as the feed), behind the scenes PieFed subscribes you to all the communities within. If the feed owner adds a community then all the feed subscribers automatically follow/join the new community too.