This is a confusing topic indeed! I am not yet very familiar with ActivityPub but as the new community manager of meta.discourse.org it appears I need to learn! 
Let me try to do that here.
We unlisted this topic here on meta.discourse.org because there appears to be a bug of some sort, not allowing the first post to be edited. That we think is related to ActivityPub and we’ve asked @angus to check into it. Let’s wait a bit to see how that gets resolved and then we can see what we want to do with this topic here on meta.discourse.org.
@jagster I appreciate your trying to help out here but please take a more polite tone with a person who is not even a member of meta.discourse.org and might not know how things work here. Likewise @strypey1 please be patient with Jagster who is a knowledgeable Discourse user who is just trying to be helpful and wants to help make Discourse better. 
@jagster is a member of meta.discourse.org but not a member of socialhub.activitypub.rocks. Meanwhile @strypey1 is a member of socialhub.activitypub.rocks but not a member of meta.discourse.org. So it’s understandable that some confusion may arise.
Looks like this topic was started at https://socialhub.activitypub.rocks/t/forum-federation-thread-on-the-socialmusic-network/5383 initially, and federated to https://meta.discourse.org/t/forum-federation-thread-on-the-socialmusic-network/370991. On socialhub.activitypub.rocks, the software > discourse category is set up to federate to the support category on meta.discourse.org. The topics are identical in both places, though not everybody participating is a member of both sites.