Alright, so I can start a thread/create a post on lemmy from hubzilla, but the behaviour’s… weird?
Hubzilla has a notion of channels that can be individual users or forum-based communities. You can share a post with public, some other fine-tuned lists, or post them on forums.
Lemmy communities correctly get recognised as forum channels. Why is it then that I still need to create a public post and tag the community channel to create a post rather than just posting and sharing with the forum channel??
TL;DR: Hubzilla forum channels = lemmy communities. Why still make public post and tag community then?

I’m not familiar with Hubzilla, but it would seem fairly trivial to make it possible to address channels explicitly in a Multiselect field somewhere, rather than it being implicit by mentioning their handle in the body. In the case of Mastodon it’s just the UX they want to go with I think