While I am not active poster/commenter on reddit, I sometimes go their to follow some stuff. Here are my favorite places with great communities that I think goes against the general low reputation of reddit.
r/patientgamers - for people who play games after many years of their release. I was always a member of this club, because I never had a gaming computer, always lagging many generations behind.
r/bioshock - covers all of the Bioshock series. Shared memories, artworks, cosplays, etc.
r/alienisolation - one of my all-time favorite game, and best horror game ever, Alien:Isolation. People still sharing tips with new players, and stuff.
r/ThisWarOfMine - It's one of my newest favorite game. You are looking after a few people of survivors during a war.
r/invisibleinc - one of the best turn-based/rogue-lite strategy games, with some futuristic spicy.
r/GOG - fans of the DRM-Free gaming shop, called GOG. If you want to support ethical gaming, you really should consider buying games only from this place.
Culture (movies, TV, books)
r/Emacs - place for sharing Emacs stuff.
r/unixporn - stupid name, but great place for inspiration and copy other people's Linux and Mac setup.
r/i3wm - my favorite window manager on Linux. If you want customization, look at the unixporn subreddit.
r/linuxgaming - mostly about Wine and DXVK stuff now, but it's still on Linux, so it counts.
r/winegaming - this should be the Wine/DXVK subreddit, but most stuff went to r/linuxgaming since it nows means Windows gaming on Linux.
r/Linux - people still care about this operating system? LoL