In those days, Voodoo cards were all the rage. There was a binary Glide library available for Linux; Mesa could link against it and give you full OpenGL (with some limitations, such as texture size) support. GLQuake and Quake 2 ran; and non-3D games could certainly have been made to run had the developers cared to. (I coaxed StarCraft into running with Wine, but it didn't have IPX support so no LAN play.) About a year later, the Quake 3 demo and eventually Quake 3 itself ran under Linux.