It's exactly GOG's thing that games sold there can't have any DRM, so this scenario is out. (Also, no disk with GOG games ;))

Probably why you won't find things like Red Dead Redeption II (PC) in GOG, since Rockstar wants to force you to register in their systems to get your sweet, sweet private info. (Curiously, the pirated version has no such anti-consumer crap)

In my experience as a gamer for almost 4 decades, the most likely scenario with a really old game is that it simply won't install or run in the OS version or even hardware that you have now, though give it enough time and somebody out there will have created an emulator or adaptor layer for it (like DOSBox).

But yeah, any game from the Phone-home DRM generation which isn't bought from a seller which has No DRM policy (which only GOG has, as far as I know - even itch.io doesn't have a No DRM policy) will almost certainly have an artificially created end-of-life that has nothing to do with the OS or hardware you have being too new for the game.