I got a Lenovo T420s with a dedicated NVS 4200M Graphics Card running Ubuntu 18.04 and want to connect to an external monitor with WQHD resolution. However, when joining displays, the external monitor's max resolution only goes up to 1920x1080 in the Displays settings:
I tried connecting with both HDMI and DP. Weirdly, when I use DP, the monitor stays dark altogether (and does only "occasionally" show up in Displays settings), but I can drag windows over to it.
What more can I do to debug this?