SUMMARY

If I scale my display, KRDC fails to detect the current correct screen resolution in connection settings, using real resolution divided by scaling factor. The connected RDP session will use that "scaled" resolution. If the real screen resolution is set manually ("Custom Resolution"), the RDP session window fits the whole screen but also shows an ugly scrollbar on the borders of the screen.

NOTE that Kubuntu package manager does not provide me with the option to try later version of KRDC.

STEPS TO REPRODUCE

1. Ensure display scale is set 1. Bring up KRDC, observe "Current Screeen Resolution" setting (3840x2160 in my case).

2.  Scale display (I use 1.6). Relog/reboot. Bring up KRDC, observe new "Current Screeen Resolution" setting (2400x1350 in my case).

3. Connect to Windows desktop for both cases, observe difference. Try to setup the real screen resolution for RDP sessionfor the scaled screen (3840x2160 in my case), connect to observe the described effect.

EXPECTED RESULT

KRDC uses real current screen resolution regardless of scale factor

SOFTWARE/OS VERSIONS
Windows: 7 Enterprise (connecting to it using RDP)
macOS: 
Linux/KDE Plasma: Kubuntu 19.10
(available in About System)
KDE Plasma Version: 5.16.5
KDE Frameworks Version: 5.62.0
Qt Version: 5.12.4
Kernel Version: 5.3.0-42.generic
OS Type: 64 bit

ADDITIONAL INFORMATION

Compositor rendering backend: OpenGL 3.1

xrandr output:

Screen 0: minimum 8 x 8, current 7680 x 2160, maximum 16384 x 16384
DP-3.2 connected 3840x2160+0+0 (normal left inverted right x axis y axis) 698mm x 393mm
   3840x2160     60.00*+  29.98    29.97    25.00    23.98  
   1920x2160     59.99  
   1920x1080     60.00    59.94    50.00  
   1680x1050     59.95  
   1440x900      74.98    59.89  
   1280x1024     75.02    60.02  
   1280x960      60.00  
   1280x720      60.00    59.94    50.00  
   1024x768      75.03    60.00  
   800x600       75.00    60.32  
   720x576       50.00  
   720x480       59.94  
   640x480       75.00    72.81    59.94    59.93  
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 connected primary 3840x2160+3840+0 (normal left inverted right x axis y axis) 346mm x 194mm
   3840x2160     60.00*+
DP-5 disconnected (normal left inverted right x axis y axis)
DP-6 disconnected (normal left inverted right x axis y axis)