Actually a few, but to list some
r/PublicDomain
r/MirrorsEdgeAesthetics
r/MovieSuggestions
r/LostMedia
rMediumReadings
r/RockinTheClassics
r/REgames
r/CarHacking could also be good
Maybe~~ r/iwatchedanoldmovie
~~
Some game specifics sub's like r/MetalGearSolid, r/MetalSlug and r/HalfLife, r/moddergearsolid is a particularly obscure one.
Most of the console modding subs like r/360hacks, r/WiiUHacks which is going dark, r/PS3Homebrew and so on.
From my own feed that's about it, with the exception of some piracy ones like rCemuPiracy r/LinuxCrackSupport and r/SteamDeckPirates, among others. And a couple in particular that push a bit closer to the work unsafe side, so those wouldn't be here.