You do know that HN in in the category of social media right?
HN is social media.
It is clear from the ruling that by including YouTube, Reddit and Facebook, they take a broad definition of what social media is, essentially anything with user interaction and Hacker News definitely fits the bill.
And if your criteria includes "social aspects like user profiles and followers", then GitHub would fit too: it has user profiles, followers / stars, and allows for discussion. It is even included in the "social media" list for ESTA and visa applications for the US. We could even include StackOverflow, I mean, it used to be common practice to build a profile, chasing a reputation score so that you could show off to recruiters.
This is not entirely correct anymore, many of the new features added to Reddit over the last 5 years have focussed on expanding precisely this aspect of the site.
You can't follow people or have followers. There's no notification system when someone "likes" your comment. It doesn't lend itself towards pulling you back with the latest comment or post. There is the front page algorithm, but you can always just go to /latest or /active. It's about the content, not the users.
Critically, there's no ads or monetization (which is where all that garbage comes in).
You cannot follow or be followed. There is no attention drawn to your username or profile. Everything about HN is designed for you to just read a comment and move on, not caring much about the human behind it.