I am new, and I am sure that the culture has changed a lot like with Mastodon in the last few years, but what I perceive is lots of FOSS and Linux people, which is unsurprising. There’s tech/infosec people like on Mastodon, and people that have what I consider a very healthy skepticism about big data, corporations, and corporate surveillance. I also notice that political attitudes have a much healthier range than any other social media I’ve been on in the last decade - and I don’t just mean that there are more people like me. There is a good number of people I disagree with, too.
There are definitely people interested in games and niche interests/hobbies, but it feels to me like the community is still very FOSS-centric. Which is nice. :)