Unreal Tournament 2k4 on one of the earlier Ubuntus, back when ShipIt was still a thing. Most have been around 2005 or 2006, as I used it in my mom's flat which I moved out of in 2006.
I also played some games on an old version of Suse Linux back in 2001 or so? Maybe earlier? There was this game where you had to manage public transport in a city. Looked for that game recently but nothing came up. Also Kartoffelknülch back then. I tried to get some distributions running (like Mandrake) but only Suse somewhat worked. Being 14 and English not being your mother tongue doesn't help with documentation when nobody in your family knows stuff about computers.
The fact that I can't seem to find traces of this game online makes me think that maybe my memory is wrong? But also hard to find information from back when the internet wasn't flooded with stuff