Ubuntu does support that GPU, it's just that you have unsupported graphics packages installed from the 'oibaf' PPA. Please uninstall the PPA using ppa-purge, or reinstall Ubuntu again without using PPAs.
Ubuntu does support that GPU, it's just that you have unsupported graphics packages installed from the 'oibaf' PPA. Please uninstall the PPA using ppa-purge, or reinstall Ubuntu again without using PPAs.