I am specifically asking about software and needed libraries, not stuff like Wikipedia or the writings of Ernest Hemmingway.
To keep people from archiving all of github on thousands of shucked external hard drives cobbled together all Frankenstein-y to create a postapocalyptic data center assume a ~1TB storage limitation. Though I’m sure that person exists here on Lemmy somewhere :D
Retro is a good starting point. You can store just about every NES game ever released in less than a GB, and the SNES isn’t that much bigger. Once you get into the 3D era you might have to be a little more selective, but you could still fit a lot of early 3D games in there.
Another way to economize space would be video game mods. Since many mods reuse the same models and textures to make a new game, you could multiply the amount of content you get per MB that way. And there are a ton of Half Life 1 mods, Thief mods, and Doom WADs out there. Gmod can run over LAN, and there’s an absolute ton of maps and game modes for that.
Finally, there are some more modern games that are remarkably small. Animal Well is only 35 MB. Gloomwood is only 2.07 GB, comparable to the size of its inspiration Thief (1998), though Gloomwood is unfinished at the moment and will probably be bigger once it’s out of early access. Shadows of Doubt is 1.31 GB. Lethal Company weighs in at 1.07 GB and can apparently be made to work over LAN. ADACA at 2.44 GB is actually smaller than its inspirations Half Life 2 and STALKER, probably by dint of having only vertex colors and no textures.