Based on this comment:
There are some anomalies in the federation between Lemmy and NodeBB. In the past, I noticed that Lemmy only federated communities/categories where at least one Lemmy user had started a conversation. Yes, I know it seems like magic, but I imagine there is a reason for it…
If what the comment said is accurate, it would be an issue if I want to subscribe to a category where I"m not supposed to create a new topic.
Speaking about the instance I’m in and specifically with respect to !technical-discussion@activitypub.space, I’m subscribed to it. So far, I only see posts that a Lemmy user or a user local to the category/community’s instance has authored.