Everything on GoG is DRM-free, simple .exe installers that should work without any servers.
I often run games outside of steam so I can let my bf use steam family share at the same time.
https://pcgamingwiki.com/wiki/The_Big_List_of_DRM-Free_Games...
I'm not a fan of Steam, so that's not a real alternative for me.
The 7" I bought when I was 10 still plays. So do the tapes I copied in school, though I've moved on from tape. The flacs and mp3s will be around as long as I have a server. I can still play Morrowind - I don't need a server up, and most -not all - online games spoil the game by being online. Quite happy with a LAN mode to play with partner or kids, or ad-hoc server mode to play WAN with friends.
Most online games have been updated so they aren't remotely the same game as they were - especially for things like MMOs, Spotify is an ephemeral radio station, Netflix is reducing what they have every month. Whether it's down to company closing, getting bored of keeping service up for an old game, or stopping your monthly sub, the rate of attrition is frightening.
It was a single player game. There was never anyone to play against. The online aspects were for DRM only.