Comment # 2 on bug 1208681 from Michael Hamilton

Further info - from when running 5.27.0:

% xdpyinfo | grep  resolution  
resolution:    161x161 dots per inch

% xrandr                                                                        
Screen 0: minimum 8 x 8, current 7200 x 2160, maximum 32767 x 32767
DP-0 disconnected (normal left inverted right x axis y axis)
DP-1 connected 3360x2100+3840+0 (normal left inverted right x axis y axis)
546mm x 352mm
   1920x1200     59.95*+
   1920x1080     60.00  
   1680x1050     59.95  
   1600x1200     60.00  
   1440x900      59.89  
   1280x1024     60.02  
   1280x960      60.00  
   1024x768      60.00  
   800x600       60.32  
   640x480       59.94  
DP-2 disconnected (normal left inverted right x axis y axis)
DP-3 disconnected (normal left inverted right x axis y axis)
HDMI-0 disconnected (normal left inverted right x axis y axis)
DP-4 connected primary 3840x2160+0+0 (normal left inverted right x axis y axis)
600mm x 340mm
   3840x2160     60.00*+  30.00  
   2560x1440     59.95  
   1920x1080     60.00    59.94  
   1600x900      60.00  
   1280x1024     60.02  
   1280x800      59.81  
   1280x720      60.00    59.94  
   1152x864      59.96  
   1024x768      60.00  
   800x600       60.32  
   720x480       59.94  
   640x480       59.94    59.93  
DP-5 disconnected (normal left inverted right x axis y axis)