Using a more recent version of xserver-xorg-video-nouveau through Oibaf's "Updated and Optimized Open Graphics Drivers" PPA (https://launchpad.net/~oibaf/+archive/ubuntu/graphics-drivers) resolves the issue for me - all three screens are working properly!
Using a more recent version of xserver- xorg-video- nouveau through Oibaf's "Updated and Optimized Open Graphics Drivers" PPA (https:/ /launchpad. net/~oibaf/ +archive/ ubuntu/ graphics- drivers) resolves the issue for me - all three screens are working properly!