osma, A few days ago I suggested that once Meta's Threads launches, its focus probably will be in groups - either public or semi-private. The details of what that could mean are in this thread.
https://social.fishpool.org/@osma@fishpool.org/posts/193897234189601792/Earlier, I asked why Strava hasn't integrated with #ActivityPub.
https://mas.to/@osma/110371213306088525Now, consider these two items in combination. A lot of athletes are sharing their training and competition diaries with fans in apps like Strava as well as Instagram. AP could link them together.