After updating to Catalina I got this message:

When I try to give this permissions I don't see the option to select karabiner_grabber:

after that Karabiner doesn't work. (no tray element, no mapping)
A dialog about karabiner_grabber is shown (may be hidden by another window).
https://pqrs.org/osx/karabiner/document.html#usage-catalina
You have to press the "Open Sysetm Preferences" button on the dialog in order to add karabiner_grabber into the list.
Please search the dialog.
After few log outs/ins I was able to see the karabiner_grabber on the list and could choose it.
Yes, minus some windows and you will see behind the Karabiner dialog another window that you can click the open system preferences and then you will see grabber. I have the latest os, Mac OS Catalina 10.15.1.
Cheers
You can use the + button to add karabiner_grabber from this location
/Library/Application Support/org.pqrs/Karabiner-Elements/bin/karabiner_grabber
I'm having a related issue, reported here: https://github.com/pqrs-org/Karabiner-Elements/issues/1867
Apologies for the cross-posting, but I'm finding it surprisingly difficult to work without the hyper key that I have depended on for the last seven or eight years. Anyone got any tricks to get Karabiner-Elements working again in Catalina 10.15.7?
Most helpful comment
You can use the + button to add karabiner_grabber from this location
/Library/Application Support/org.pqrs/Karabiner-Elements/bin/karabiner_grabber