You can check for any instance who they have federated with and who they have blocked by navigating to their /instances page. For example for Beehaw: https://beehaw.org/instances

That link is showing lemmy.world as blocked. I'm still new to all this but isn't that a reputable instance?

Explained here: https://beehaw.org/post/567170

TL;DR: Beehaw does not currently have the resources and/or tools that they feel are necessary to moderate the incoming users from lemmy.world.

Well shit, I guess I gotta leave beehaw because now half my subscriptions are dead now.