I loved the writing subs. Reading short stories and encouraging eachother to grow.

People to talk to about things that annoy my wife lol. Mainly linux stuff.

1. Tech support that isn't an advert (Reddit was a goldmine for more interesting hardware)

2. Cool stats/maths things to share with my students

3. Snek and Fox pictures to get me through my marking sane(ish)

Niche stuff. I mostly came to reddit for discovering interesting/weird/rare plants and the best way to care for them. Googling has become absolute dogshit with obviously generated articles that are just parroting the same information (which for niche plants, can be false, speculation, and even harmful).

I'm in a couple of Discord communities (which have jumped up in activity in the last couple of days), but those communities are a bit harder to find that four year old post about "what does this type of growth mean", or something similar.

I also used reddit for tracking technology issues in much the same way - very specific, hard to locate issues that only a few people might be experiencing and talking about in a searchable way. Everything from video games, to work related technologies.