I agree, it is always HTTP nowadays. The Librecast project [0] is doing interesting R&D around multicast and social networking, and has been / is being funded by multiple NLnet grants over the years. I think they have plans to use ActivityPub to demonstrate their work. Current active project is LibreCast Studio, a collaboration environment. The linked video on the page is a very interesting watch.

[0] https://librecast.net/about.html