Corroded

I think it’s going to get more and more challenging due to how many games are focused on online play. If co-op or multiplayer servers are shutdown a lot of the time it comes down to fans to recreate them.

I’d highly recommend checking out this PCGamingWiki page about GameSpy server replacements if you are into that kind of thing.

Even with these mods you still run into the issue of needing either players or bots and whether or not to archive all game altering updates.

I would say MagiPacks might be an even better example primarily because they deal with older games. They also operate along the GOG logic of ensuring games run on modern operating systems but they do it by bundling in commonly used fan patches.