Lots of Linux games on rutracker, new games appear regularly:
Almost all of them just werk, but some require you to hunt down missing dependencies. Run ldd on the executables to find what libraries you're missing.
Check the descriptions, some of them mention the required hardware. If unclear, check also store.steampowered.com.
The stated requirements are not always reliable though, I've managed to get games working that officially require newer hardware.
Some useful tricks:
- run executables with the "-force-opengl" flag for better performance / working at all. AFAIK this works only for Unity-based games.
- if you have old GPU that doesn't support newer OpenGL versions you can sometimes
use (for example) MESA_GL_VERSION_OVERRIDE=3.3COMPAT environment variable to get them working
- LIBGL_ALWAYS_SOFTWARE=1 env variable will use software rather than hardware rendering. Sometimes makes a huge difference, but your CPU will quickly overheat.
- lots of games leave logs somewhere. In my experience if the game doesn't work it's because the GPU is too old. For Unity games look at ~/.config/unity3d/