Is there an open-source decentralized alternative to HN?

A personally curated RSS feed list is about as distributed a system as you'll find, and you can keep the S/(S+N) level as high as you're willing to work for.

Comments take days, weeks, or years to show up though.

HN is often compared to Reddit, and the self-described "open-source federated Reddit alternative" Lemmy[0] also compares itself to Hacker News[1]:

Lemmy is similar to sites like Reddit, Lobste.rs, or Hacker News: you subscribe to communities you're interested in, post links and discussions, then vote and comment on them. Lemmy isn't just a reddit alternative; its a network of interconnected communities ran by different people and organizations, all combining to create a single, personalized front page of your favorite news, articles, and memes.

* FWIW, I have no experience with Lemmy beyond seeing it pop up here on HN from time to time[2].

[0] https://github.com/LemmyNet

[1] https://dev.lemmy.ml/

[2] https://hn.algolia.com/?q=lemmy