External monitor HDMI does not work with Intel HD5500 (Ubuntu 16.04)

Question

I'm having trouble getting my external monitor working with my Asus R556LA which has the Intel HD5500 integrated graphics on Ubuntu 16.04. The issue started appearing a few days ago, and before that period I had no issues whatsoever with using the monitor. When I connect the monitor with HDMI, Ubuntu does not recognize it in the "Display" section and the monitor itself keeps switching from analog to HDMI output.

Here's the output I'm getting by running lshw -c video:

sudo lshw -c video
  *-display               
       description: VGA compatible controller
       product: Broadwell-U Integrated Graphics
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 09
       width: 64 bits
       clock: 33MHz
       capabilities: msi pm vga_controller bus_master cap_list rom
       configuration: driver=i915 latency=0
       resources: irq:48 memory:f6000000-f6ffffff memory:e0000000-efffffff ioport:f000(size=64) memory:c0000-dffff

The kernel version I'm running is 4.8.0-56-generic. I've found that the Intel integrated graphics are part of the kernel which leads me to believe that a kernel update might've wrecked the drivers for me. I've tested the monitor on another setup to rule out that the monitor was broken.

EDIT: For some reason it does seem to be working when I connect it with a VGA cable. I tried other HDMI cables to see if it was the cable but no luck there either. I'd like to get the HDMI cable working as VGA only allows resolutions up to 1024p while HDMI can use a higher resolution (1080p in my case).

EDIT2: Here's the output of xrandr with VGA plugged in:

Screen 0: minimum 320 x 200, current 2390 x 768, maximum 8192 x 8192
eDP-1 connected primary 1366x768+0+0 (normal left inverted right x axis y axis) 344mm x 193mm
   1366x768      60.03*+
   1360x768      59.80    59.96  
   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 1024x768+1366+0 (normal left inverted right x axis y axis) 0mm x 0mm
   1024x768      60.00* 
   800x600       60.32    56.25  
   848x480       60.00  
   640x480       59.94  
HDMI-1 disconnected (normal left inverted right x axis y axis)

And here it is with HDMI plugged in:

Screen 0: minimum 320 x 200, current 1366 x 768, maximum 8192 x 8192
eDP-1 connected primary 1366x768+0+0 (normal left inverted right x axis y axis) 344mm x 193mm
   1366x768      60.03*+
   1360x768      59.80    59.96  
   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 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)

Answer 1

I ran into this problem today on Ubuntu 18.04. The solution was to completely disconnect and turn off the monitor then reboot the computer and finally connect the monitor and turn it on. Somehow it seems to fix the problem.

Here is a similar solution

Answer 2

I recently ran into this issue with Ubuntu 17.10 and 18.04, and Linux Mint 18.03 with my Dell Latitude E7470 Laptop. The kernel that worked to restore HDMI for me was 4.15.18-041518-generic. I installed it using the ukuu tool from https://launchpad.net/~teejee2008/+archive/ubuntu/ppa .