https://help.ubuntu.com/community/Games/Native/UnrealTournament#Troubleshooting

Error loading shared libraries

If you get an error when you run the .run file that looks like this:

error while loading shared libraries: libgtk-1.2.so.0: cannot open shared object file: No such file or directory

You will need to install the old libgtk along with its dependencies. The next few steps assume you are using a processor compatible with i386 architecture. To download the library and its dependencies:

wget http://archive.ubuntu.com/ubuntu/pool/main/g/gtk+1.2/libgtk1.2_1.2.10-18_i386.deb && wget http://archive.ubuntu.com/ubuntu/pool/main/g/glib1.2/libglib1.2_1.2.10-10.1build1_i386.deb && wget http://archive.ubuntu.com/ubuntu/pool/universe/g/gtk+1.2/libgtk1.2-common_1.2.10-18.1build2_all.deb

Install them

sudo dpkg -i libgtk1.2-common_1.2.10-18.1build2_all.deb && sudo dpkg -i libglib1.2_1.2.10-10.1build1_i386.deb && sudo dpkg -i libgtk1.2_1.2.10-18_i386.deb