SUMMARY
I've upgraded from 5.16 to 5.18 recently, and shortcut Meta for Kickoff did not
work from the get go.  I've been struggling to make Meta work for Kickoff (the
whole Alt+F1 workaround thing) after upgrading from 5.16 to 5.18. Now Meta for
Kickoff works. But shortcuts Meta+[number] and Meta+[letter] stopped working.

STEPS TO REPRODUCE
1. Open "System Settings > Workspace > Shortcuts > Global Shortcuts > Other
   Shortcuts > Activity switching"
2. Make sure "Activate Task Manager entry" one through ten have shortcuts
   Meta+1 through Meta+0 respectively.
3. Make sure shortcut "Activities..." is set to Meta+Q (also tried Meta+A and
   Meta+Shift+A)
4. Press shortcuts from steps 2 and 3 right there in the "System Settings"
   dialog window.
5. Change "Activate Task Manager entry" to something without Meta key, like
   Ctrl+Shift+2

OBSERVED RESULT
- In Step 4 digits and letters are typed in the "Search..." field of the System
  Settings dialog in the top left.
- In Step 5 nothing happened.

Please note, that the settings dialog understood and recorded the shortcuts
while focus was in the button "Input..." perfectly fine.

EXPECTED RESULT
Action corresponding to the shortcuts are launched.

SOFTWARE/OS VERSIONS
Operating System: Kubuntu 20.04
KDE Plasma Version: 5.18.4
KDE Frameworks Version: 5.68.0
Qt Version: 5.12.8
Kernel Version: 5.3.0-51-generic
OS Type: 64-bit
Processors: 8 × Intel® Core™ i5-8250U CPU @ 1.60GHz
Memory: 7.7 GiB of RAM

ADDITIONAL INFORMATION
- Following Meta shortcuts work:
  - Meta+L to lock the session
  - Meta+F7 to toggle touchpad
  - Meta+D to show desktop
  - Meta+. for Emoji selector
  - Meta+E for Dolphin
- Shortcuts for "Walking through activities", which is also in the "Activity
  switching" group works.
- I probably did mess something up while trying to get Kickoff shortcut working.
  I just don't remember what I did exactly.  I'll be happy to provide any
  configuration file.
- I've also tried setting the shortcuts in "Global Alternate" column, which
  also did not work.