I just got a new 4k monitor LG-27UL500, I am using Ubuntu 18.04.5 LTS but I can't set the resolution higher than 1920*1080. There a some similar threads about this topic (this one for example), but none of them seemed to work for me.

Maybe it could be because my GPU has a mini-display port connector, and I'm using an adapter to connect to the HDMI of the monitor?

Here are my specs:

OS: 18.04.5 LTS

GPU: NVIDIA Corporation GP107GL, Quadro P620 , output = mini-display port

Monitor: LG27UL500, input = HDMI

GPU drivers (got with dkms status):

nvidia, 510.39.01, 4.15.0-167-generic, x86_64: installed

nvidia, 510.39.01, 4.15.0-169-generic, x86_64: installed

nvidia, 510.39.01, 4.15.0-171-generic, x86_64: installed

nvidia, 510.39.01, 4.15.0-173-generic, x86_64: installed

nvidia, 510.39.01, 4.15.0-175-generic, x86_64: installed

nvidia, 510.39.01, 5.4.0-104-generic, x86_64: installed

nvidia, 510.39.01, 5.4.0-105-generic, x86_64: installed

nvidia, 510.39.01, 5.4.0-107-generic, x86_64: installed

UPDATE 1:

Someone suggested that the problem could be an outdated GPU driver. So I tried to manually download drivers from NVIDIA website and install them. Unfortunately, this is the message that I get:

I tried to install the drivers as soon as I started the PC, but it did not change.

UPDATE 2:

Here is the output of my xrandr -q:

Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 32767 x 32767

DP-0 disconnected (normal left inverted right x axis y axis)

DP-1 disconnected (normal left inverted right x axis y axis)

DP-2 disconnected (normal left inverted right x axis y axis)

DP-3 disconnected (normal left inverted right x axis y axis)

DP-4 disconnected (normal left inverted right x axis y axis)

DP-5 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 600mm x 340mm

   1920x1080     60.00*+  59.94    50.00    29.97    23.98  

   1600x900      60.00  

   1280x1024     60.02  

   1280x800      59.81  

   1280x720      60.00    59.94  

   1152x864      60.00  

   1024x768      60.00  

   800x600       60.32  

   720x576       50.00  

   720x480       59.94  

   640x480       59.94    59.93  

DP-6 disconnected (normal left inverted right x axis y axis)

DP-7 disconnected (normal left inverted right x axis y axis)

  3840x2160_24.00 (0x2e9) 266.750MHz -HSync +VSync

        h: width  3840 start 4056 end 4456 total 5072 skew    0 clock  52.59KHz

        v: height 2160 start 2163 end 2168 total 2192           clock  23.99Hz

  3840x2160_60.00 (0x367) 712.340MHz -HSync +VSync

        h: width  3840 start 4152 end 4576 total 5312 skew    0 clock 134.10KHz

        v: height 2160 start 2161 end 2164 total 2235           clock  60.00Hz

However, if I try to activate the 3840x2160 mode with command xrandr --addmode DP-5 3840x2160_60.00 (or 24.00 instead of 60.00), this is what I get:

X Error of failed request:  BadMatch (invalid parameter attributes)

  Major opcode of failed request:  140 (RANDR)

  Minor opcode of failed request:  18 (RRAddOutputMode)

  Serial number of failed request:  43

  Current serial number in output stream:  44

I still have to try with a cable without adapter, I hope I can find one today!