Devs running their own PDS hosts are still unable to federate on the production network, for the time being. The dev sandbox will of course remain online indefinitely. The major scaling push continues, but things are progressing rapidly!

Aren't the feeds the instances themselves?

One way to think of it: Feeds are "Algorithmic Federation" (anyone can run a server that provides a custom feed) PDS hosts are "Data Federation" (anyone can run a server that hosts accounts with their posts/likes/etc)