If you're a software developer who wants to work with the ActivityPub protocol in any way, there are discussion forums and lots of resources on this website:
The site is run by the people who created and maintain the ActivityPub standard.
(For any non-techy people reading this, ActivityPub is the technical standard that is used by Mastodon and the wider Fediverse to allow people on different servers to follow and interact with each other.)
