It doesn't look like there's any federation right now, the test site (https://dev.lemmy.ml/) says "Federation into the ActivityPub network is on the roadmap."
Leaving it to last makes me worry that it won’t happen.
Not federated yet either unfortunately. But I think one of the few fediverse projects that dogfoods ActivityPub by using the client to server protocol to communicate between frontend and api.
I get that somebody probably needed to do this work of standardization. As a project it seems to lack imagination, though. There is nothing to get excited about as far as I can see. It's just a consolidation of very familiar social media functions.