2 as of today. My main is on BeeHaw, but I realized that some of the communities I wanted to follow were on defederated instances, so I signed up for programming.dev. I think I'm going to use it for the tech-related communities (plus anything defederated) and BeeHaw for the rest
A specific instance (like BeeHaw) can defederate other instances. It's basically like blocking that instance so users on BeeHaw can't interact with that instance.