Lemmy currently supports only inter-Lemmy federations, and the Lemmy developers are thinking of federating with Fediverse in the future, but that will be a long way off. So, it is not possible. At least not yet.
This is only partially correct.
There is some ongoing efforts to enable community (groups) federation to other systems, the problem is that very few other ActivityPub based software have groups/communities as a concept.
For federating user-accounts, yeah that seems a bit off as it really isn’t the focus of Lemmy.
Group vs Person is not a big deal, its just a single json field thats named differently. The problem is that each software implements a slightly different subset of activitypub, because there are many different ways to do the same thing. So these incompatibilities need to be fixed.
The other day I noticed that Mastodon federates PeerTube channels as Groups that you can follow. On the Profile you can see this displayed as a ‘Group’ label (in the web interface). Don’t know how other microblogging apps handle this.
This is an excellent opportunity to create a brainstorm topic for that in Fediverse Futures, so here goes:
🚀 Ideas for federating Lemmy to the Fediverse