If you haven't done so, you should go over the content of the other Linux FAQs on this server. This FAQ doesn't duplicate answers that are common to all Q3 technology game ports.
Current topicsEvilTypeGuy reports that if you are using the FireGL drivers version 2.9.12, r_ext_compiled_vertex_array 1 (the default) can cause application hitching and freezing under heavy geometry load. You should run with +set r_ext_compiled_vertex_array 0.
NOTE: The FireGL drivers are not the official drivers. But you might be using them if you have a radeon 9800 pro / XFree 4.3
FireGL drivers page
Official ATI drivers page
Some Red Hat 9 setups fail to start Enemy Territory with an error about TLS during OpenGL init. This happens because you are loading /usr/lib/tls/libGL.so.1, which seems to have ABI issues. You should use the /usr/lib/libGL.so.1 one, by using +set r_glDriver /usr/lib/libGL.so.1
The setup crashes with Segmentation fault "$setup" "$@" 2>/dev/nullSee the related answer in the q3a FAQ.
Setup and execution on 64 bits CPUsSee the related answer in the q3a FAQ.
LinksThe Linux Gamer's faq is a very good resource for general Linux Gaming topics.