Steam sales:
Humble bundle deals:
GOG giveaways:
itch.io’s existence:
FOSS games:
Modded total conversions of existing games:
Browser/F2P games:
I mean libraries are awesome, but let’s not say pirating is the only option to get content on PC for cheap/free.
Sounds like all you gotta do is wait then, since your hyper-niche scenario will become a lot less niche once that happens.