Mastodon and Bluesky have very different architectures, and go about their decentralization and federation strategies very differently. Bluesky don’t really have the same concept of “instances” as Mastodon. Unless you recreate Bluesky’s entire technology stack, their decentralized bits typically run into some centralized linchpin that Bluesky still controls. There’s some efforts like Blacksky trying to create meaningful alternatives in the Bluesky ecosystem, but they’re still largely just proof of concept.