#Discourse also implementing #ActivityPub (joining the Fediverse) is great news! Thanks for sharing!
Here is a forum thread with more details on it. The linked post contains links to other related threads.
https://meta.discourse.org/t/federation-support-for-discourse/90921/7
@floppy it was @how with a mention of @NGIZero #funding opportunities who got the ball rolling.
https://meta.discourse.org/t/using-discourse-as-a-social-media-platform/202133/12
We've both been keeping the #ActivityPub support issue warm at #Discourse for a time. Where before the interest dealt with native AP support, I think now there's plugin developers interested in picking this up.
Hellekin may know more background information.