UT2004 is wayyyyy more lax on the 3d requirements than UT2003. It's more of a CPU hog though... Also having an OpenGL renderer unintentionally helps the 3dfx compatibility (though this reduces some effects like shadows as they were never implemented for it). You'll have to fiddle with UT2004.ini and de-semicolon one line that says OpenGLDrv and semi-colon the other that says D3DDrv
A Voodoo3 can run UT2004 too 😀 A Voodoo2 also "can" though it'll really thrash and break on rendering a lot of things even with MesaFX. Voodoo3's the sane min for this one for having the texture cache neccessary for minimum detail and even that has some rendering issues (stretchy health pickup verts anyone?)
Hell, even PCem could run it. This was a v12 WIP though around when the V2 first started to get emulation, should try this in Ironic on v14 soon.