Inside was a instruction sheet informing Linux users how they could use CVS to pull and compile 3D support, depending on their distribution. I thought it was rather funny that someone felt they could market a game to people who were compiling their own operating system. I guess that's why it was in the discount bin.
1. Wikipedia lists the release dates for the full game, which were in Dec 1999 for both Windows and Linux (windows a few weeks earlier). I don't recall exactly when the demo came out, but I think it was sometime in the winter of 1999.
Otherwise you're right, setting up Linux Gaming computers with working OpenGL Hardware Acceleration was painful, especially for us poor people who could not afford the most expensive OpenGL Hardware. ;) On the other hand I think audio was easier to setup :P
For me, it was a great first trip to Linux-Land - I was in my gaming-and-hacking phase, so I hacked together a Linux that could actually run UT :).