SUMMARY

Desktop/Panel icon widgets are no longer opened when clicked on.

STEPS TO REPRODUCE
1. Create an icon on the desktop (in "Desktop" layout) or in the panel by dragging a file or folder to it and choosing 'Add icon' from the pop-up menu.
2. Click on the icon to open it.

OBSERVED RESULT

First time:

A dialog window appears:
Warning -- Plasma
This will start the program
------
|Foo |
|    |
------
If you do not trust this program, click Cancel
Buttons: Continue Cancel

After clicking Continue, and immediately on every subsequent attempt to open:

Notification:
Plasma Desktop Workspace
Launching Foo (Failed)
The desktop entry file
/home/james/.local/share/plasma_icons/Foo.desktop
is not valid. 


EXPECTED RESULT

The folder or file should be opened, as it is in version 5.19.5

SOFTWARE/OS VERSIONS
Operating System: Arch Linux
KDE Plasma Version: 5.20.2
KDE Frameworks Version: 5.75.0
Qt Version: 5.15.1
Kernel Version: 5.4.73-1-lts
OS Type: 64-bit
Processors: 4 × Intel® Core™ i5-7260U CPU @ 2.20GHz
Memory: 15.5 GiB of RAM
Graphics Processor: Mesa Intel® Iris® Plus Graphics 640

ADDITIONAL INFORMATION

Right-click context menu works properly, including offering "Open with..." the right application.