I picked up UT99 purely because I'd heard it could run Nativity in linux. Problem is I've seen no clear howto for the gog version after an hour of fumbling about with google. I've heard conflicting things for ubuntu. That it'll work fine, that you need to install some old packages for 11.04.

Someone mind giving me the skinny so I can be on my way please?

There's a How-To for the steam variant here, I believe it shouldn't be all to different from the gog version.

[url=http://www.pcgamingwiki.com/wiki/Unreal_Tournament#Linux%20(null]http://www.pcgamingwiki.com/wiki/Unreal_Tournament#Linux%20(null[/url])

No matter what I'd do a wine installation first, so it'll run in any case. Since I used a CD version I can't help you all to much, but if the above link helps a bit, but you stumble upon problems, just post them here, I'll try my best to help you :D