Mostly it's for general overall awareness of the various things I'm interested in. It's a far more permissive environment for blowing off some steam.
The various tech subreddits are also useful. Some others, in no particular order:
r/fire
r/digitalnomad
r/design
/r/askhistorians, /r/askscience, /r/whatisthisthing, /r/legaladvice (or rather the one specific to my country), /r/manufacturingporn
For anything tech related I stay on HN
There were a few more suggestions in the HN thread as well [1] and on Twitter [2].
[0] https://notes.eatonphil.com/high-quality-subreddits-you-shou...
[1] https://news.ycombinator.com/item?id=29450583
[2] https://twitter.com/phil_eaton/status/1467536007448965129
/r/streamentry
/r/slatestarcodex
/r/emacs
Two here require some explanation: Redscarepod is for folks who listen to the Red Scare podcast, though I’d guess 30% of that subreddit listens regularly. It’s my favorite cultural subreddit.
Streamentry is meditation subreddit with focus on attaining enlightenment.
Surprisingly good signal-to-noise ratios for all of them.