I am using Dell XPS 13 9360 with Ubuntu 16.04. It does not have a HDMI slot, so I have a USB-C-to-HDMI adapter, which is then connected to my monitor: DELL S2240L.
System Settings > Displays, I can see that the monitor is detected properly and is turned on. If I try to move my mouse cursor out of my laptop screen and into the external display area, I can see the cursor leaving my laptop screen. If I keep moving my cursor further away and try to move back, it takes some time to reappear onto my laptop screen, so there is even the display 'space' for the cursor to move to.
However, the monitor keeps saying "no signal" and therefore goes to power-saving mode. I am pretty sure that the adapter doesn't have a problem because the computer is detecting the monitor. The monitor also works fine when connected to a different (Windows) desktop.
Here is the result for running
sudo lshw -C video :
*-display description: VGA compatible controller product: Intel Corporation vendor: Intel Corporation physical id: 2 bus info: pci@0000:00:02.0 version: 02 width: 64 bits clock: 33MHz capabilities: pciexpress msi pm vga_controller bus_master cap_list rom configuration: driver=i915 latency=0 resources: irq:286 memory:db000000-dbffffff memory:90000000-9fffffff ioport:f000(size=64) memory:c0000-dffff
Screen 0: minimum 320 x 200, current 3840 x 1080, maximum 8192 x 8192 eDP-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 294mm x 165mm 1920x1080 59.93*+ 1680x1050 59.95 59.88 1600x1024 60.17 1400x1050 59.98 1280x1024 60.02 1440x900 59.89 1280x960 60.00 1360x768 59.80 59.96 1152x864 60.00 1024x768 60.04 60.00 960x720 60.00 928x696 60.05 896x672 60.01 960x600 60.00 960x540 59.99 800x600 60.00 60.32 56.25 840x525 60.01 59.88 800x512 60.17 700x525 59.98 640x512 60.02 720x450 59.89 640x480 60.00 59.94 680x384 59.80 59.96 576x432 60.06 512x384 60.00 400x300 60.32 56.34 320x240 60.05 DP-1 connected 1920x1080+1920+0 (normal left inverted right x axis y axis) 476mm x 267mm 1920x1080i 60.00* 50.00 59.94 1280x1024 75.02 60.02 1152x864 75.00 1280x720 60.00 50.00 59.94 1024x768 75.03 60.00 800x600 75.00 60.32 720x576 50.00 720x480 60.00 59.94 640x480 75.00 60.00 59.94 720x400 70.08 DP-2 disconnected (normal left inverted right x axis y axis)