Tente isso para instalar o OpenGL:
sudo apt-get install libgl1-mesa-dev
O Steam não inicia, recebo esta mensagem
crazyfrog@crazyfrog-desktop:~$ steam
Running Steam on ubuntu 15.04 64-bit
STEAM_RUNTIME is enabled automatically
Installing breakpad exception handler for appid(steam)/version(1433441724)
libGL error: unable to load driver: nouveau_dri.so
libGL error: driver pointer missing
libGL error: failed to load driver: nouveau
libGL error: unable to load driver: swrast_dri.so
libGL error: failed to load driver: swrast