Lemmy.ml has now blocked Threads.net
Technically, communities/magazines aren’t an activitypub thing. The way it’s implemented, Mastodon (for example) sees a community as just another user.
A post in that community looks like a “toot” from the community user. Comments in that thread look like replies to the toot.
They are actually, communities are ActivityPub groups, the issue is that Mastodon does not implement groups (but it is soon!), so what the Lemmy group has to do is boost all the posts/comments so that people can see them in Mastodon.
Once Mastodon gets groups though, the experience should be much better.