Unfortunately I don't have that laptop anymore. Currently I have Dell Precision M5520 with Ubuntu 16.04 pre-installed and almost everything is working excellently with its TB16 dock. (3440x1440 resolution through HDMI is not always working at first try, but after disabling and enabling few times the external display from System Settings > Display, it starts to work. But that might be some hardware or cable issue.) I am using mainline kernel v4.12.5 installed with Ukuu. 18.8.2017 22.41 "Mika Westerberg"