You can also follow libraries and channels from other Fediverse applications and they basically work like RSS feeds. So, like, you can grab a channel actor id from an instance (so to use open.audio as an example again, grab one from the channels list at the bottom of https://open.audio/library). When you click into it you’ll see it’s actor name ([channel]@open.audio), which you can search for from other fediverse applications like Mastodon to follow like any other account.
It does indeed use ActivityPub!
My instance federates with the open.audio instance, for example. You can take a library or channel on an instance you want to federate with (such as https://open.audio/library/ce1fb6d4-fae6-464a-a34a-bdd46209ee82/), search for it from your local instance, and follow it.
You can also follow libraries and channels from other Fediverse applications and they basically work like RSS feeds. So, like, you can grab a channel actor id from an instance (so to use open.audio as an example again, grab one from the channels list at the bottom of https://open.audio/library). When you click into it you’ll see it’s actor name ([channel]@open.audio), which you can search for from other fediverse applications like Mastodon to follow like any other account.