I installed steam on Ubuntu Mate 15.10, and i cannot open it. I opened system monitor and I saw steam running, so i closed it and I reopened it and nothing. Its status is sleeping if that helps. I opened it in terminal and heres the output.
Running Steam on ubuntu 15.10 64-bit
STEAM_RUNTIME is enabled automatically
Installing breakpad exception handler for appid(steam)/version(0)
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