Over the last few days, I updated the current entries on this wikipage about blockchain-related social media projects;
https://wiki.p2pfoundation.net/Blockchain_Social_Media_Apps
About 1/3 of the projects in the list are still active in some form. None of them seem to have achieved a critical mass of use outside the bubble universe of crypto. Only one has now implemented ActivityPub (and previously Matrix for their in-house chat), and that one never pitched itself as decentralised.