Is HN Press?

I can tell you that the press sometimes looks at HN for material, anyway. Several years ago I made a comment on HN, and it got seen by someone at the New York Times who asked me to write an opinion piece based on it: https://www.rosshartshorn.net/stuffrossthinksabout/nyt_opini...

But, "the press" is normally considered to be content generated by people doing that for a living (albeit not necessarily a good one), and most HN contributors do other things for a living.

It is an important part of the world's media ecosystem.

Like much of the rest of the serious (not pure entertainment) part of the ecosystem, its importance might decline soon as AI services get better, but I have seen no signs of that yet.

No.

There's no standard definition of what constitutes the press.

Now, if the question is some flavor of: Do Hacker News posts and comments enjoy First Amendment protections generally described as "freedom of the press?" Absolutely.

The press isn't a special class under 1a; "or of the press;" in the First Amendment simply means you're free to write and publish -- not just speak -- without interference from the government.