I can only have 10 Favorite domains. Where to fit all the other domains I am interested in?
Account settings > Follows and subscriptions > Domain subscribes > ADD NEW DOMAIN SUBSCRIPTION
I can choose to merge the feed from the domain into my Home feed, or any existing List feed, or add a new List feed for it. The new List option will create a List titled by the domain.
At first nothing will show, because this only subscribes to future toots, not past toots. To see past toots I still need to add the domain to your Favorite domains, or go to the site directly.
The Federated feed is a feed of domains chosen by my mods. With domain subscription I can build my own "federated feed" with domains I choose.