When starting Karabiner-Elements for the first time I'm asked to add karabiner_grabber and karabiner_observer to "Input Monitoring" in System Preferences. But in my System Preferences that entry is called "Surveillance de l'entrée" and there is no karabiner_grabber and no karabiner_observer. And as I don't where these are located I cannot add them manually either. Could you please fix that?

I ran into this issue today, Catalina 10.15.6, ended up one must restart the computer to make both grabber and observer working, once rebooted, internal keyboard will be detected and imported complex modifications started working.