This is Drupal 10. I also have a WordPress site that's testing the same things ... basically ActivityPub. So this is the Drupal Angle as I use BackdropCMS (which is a Drupal 7 fork). As experiments goes, I only have a little time to keeping an eye on just a sliver of the ActivityPub developments ... but it is pretty interesting.
Let's see if I can go and figure this out.
Here's mind smashing detail about ActivityPub if you like.