If you can filter out these things, /g/ does have a lot of discussion, but it is very different from Hacker News.
It is better than /biz/, though, which is just MLMs and bad crypto advice it seems.
https://www.reddit.com/r/AskHistorians/
https://www.reddit.com/r/DaystromInstitute/
https://www.reddit.com/r/skeptic/
https://www.reddit.com/r/financialindependence/
Also, if you're feeling down at any point, https://www.reddit.com/r/babyelephantgifs/ always does the trick.
https://www.reddit.com/r/ArtisanVideos/
https://www.reddit.com/r/WatchPeopleCode/
https://www.reddit.com/r/smallbusiness/
https://www.reddit.com/r/battlegifs/
https://www.reddit.com/r/DepthHub/ , https://www.reddit.com/r/Excelsior/ , https://www.reddit.com/r/TrueReddit/
https://www.reddit.com/r/curiosityrover/
https://www.metabunk.org/current-events.f52/
The Oroville Dam discussion was particularly useful