Now that people are upset with the direction of Twitter, Mastodon has been gaining a lot of traction - and Mastadon is using ActivityPub.

It may not necessarily be particularly useful to implement ActivityPub into Composr. Composr is not a social network (it's for website and STRUCTURED communities), and we implement various standards that can be used to bridge into networks using ActivityPub...

Turn microformat web content into a Fediverse server: https://fed.brid.gy/
Turn RSS feeds into a Fediverse server: https://github.com/dariusk/rss-to-activitypub
Syndicate microformat web content across social media: https://brid.gy/
Syndicate RSS content into Mastodon: https://github.com/groundcat/mastodon-rss-bot & https://gitlab.com/chaica/feed2toot

There is a standard "MicroPub" by the same committee as ActivityPub, for publishing changes rather than syndicating them. I don't think it has gained traction but wanted to mention it. I guess the idea is divorcing frontend from data, but that doesn't seem very important to me TBH, and I think you'd have a hard-time decoupling them and still having a good experience.

Here's an interesting discussion which may be relevant: https://github.com/diaspora/diaspora/issues/7422#issuecomment-451750994