MetaFilter! It's an old-school text-only community blog that's been around since 1999. I love the variety and depth of posts on the front page, and the AskMetaFilter Q+A section is super useful.
Metafilter has some good conversations and unique content for threads.
From the same era, and with similar interesting levels of content was kuro5hin.org (aka. corrosion , Now offine) and everything2.com (a massively interlinked set of nodes created before wikipedia).
It's an organic community, small enough and long-lasting enough that it's easier to get to know people as people instead of as names on a screen you'll see once and likely never again. The admin team is similarly small and easy to talk to, not an algorithm or a faceless corporate enforcer. The mods are paid professionals funded largely by community donations. The site is also in the process of transitioning to a non-profit management, so less risk of selling out or enshittifying itself. I like the posting and commenting culture -- text-heavy, minimalist style, and a wide variety of topics often deeply researched and explored in lengthy posts by people passionate about the topic, rather than 24/7 outrage-bait headlines and viral videos. And the subsites are really fun -- I mentioned AskMeFi, but there's also a place to share one's music, personal projects, discuss media, organize meetups, etc. I also appreciate how the mods and guidelines take a strong stance against bigotry and microaggressions -- hate speech and spam are virtually unheard of. Very refreshing when the bigger platforms seem intent on pursuing growth at all costs and minimizing administrative overhead. Overall, a cozy, human-scale community that seems more and more like a throwback that we should be moving back to.