You're here on a forum that is outside the usual centers. The centralized equivalent is /r/programming and you are not there. Why?
I'm not aware of an actually decentralized equivalent of what Hacker News is (basic threaded text forums) but that might be an interesting project for someone to build on an existing protocol.
the second link goes directly to the largest instance. It has all the same federated interoperability features that Mastodon or Bluesky have, but with a thread/topic format instead of a microblog format.
You may be thinking of distributed systems, like blockchains, which have no centers at all. Nobody is using those for social media yet.
The "center" that matters in this context is the server and owning entity, not the taxonomy of the content. Decentralized platforms aren't owned and operated by a single entity, centralized platforms are. You can't just spin up a new instance of Hacker News with different moderators and just federate with it, because "Hacker News" as a network is entirely owned and controlled by YCombinator. Not so with, say, "Mastodon."
Also yes unfortunately there are already multiple blockchain-based social media platforms.
unless you actually meant /g/ :)