SUMMARY

Keyboard input is misbehaving in Folder View widgets placed onto the desktop. 
Most keys don't react and some incorrectly.

STEPS TO REPRODUCE
1. Create a Folder View widget on a desktop
2. Click on any file
3. Try to navigate with the arrow keys
4. Try to delete the file using the delete key
5. Hit the shift key to make a multi-selection with a file that is on the left of the first one

OBSERVED RESULT

3. The cursor doesn't move when hitting arrow keys.  
4. The file is not deleted when hitting the DEL key.
5. The selection is incorrect. 
For instance, I have 2 rows of 3 files. If I click on the last file, then hit shift, then click on the file on its left, instead on having 2 files selected I have 5 files selected.


EXPECTED RESULT

3. Arrow keys would enable to change the selected file / move the cursor
4. Hitting DEL would put the selected into the trashcan
5. Selecting a file, then hitting SHIFT, then selecting the file on its left would select those 2 files


All this is probably due to the recent changes which make it possible to navigate in a folder view put into a panel and not onto a desktop.


SOFTWARE VERSIONS
(available in About System)
KDE Plasma Version: 5.14.0
KDE Frameworks Version: 5.55.0
Qt Version: 5.11.1

ADDITIONAL INFORMATION
KDE Neon 18.04