If you visit this site often, you’ll find many many links to projects on GitHub and not just mine. One of the thing I like about GitHub is how easy it is to search for stuff. So I put games in the top left search box and then ticked the C checkbox.

That returned 2,569 results but not all are playable games. Some are one off projects for other hardware such as Wii, GameBoy, Switch and similar. One gem I found was BSDGames. This is quite old and the 43 games are text based including the original Adventure.  I get the feeling many of these are from the Basic Computer Games books but at least these are in C not BASIC.

These will probably compile better on Linux and with difficulty and lots of fixes on Windows. And yes there is a Tetris game in the collection!