Plasma 5.17 beta Discover system updates regression

[Richard Ullger]

Since upgrading to plasma 5.16.90 from the Arch kde-unstable repo, Discover is 
checking for system updates by default and I cannot find where to disable this 
behaviour. I've checked in Autostart and Background Services in System 
Settings -> Startup and Shutdown and in system tray settings. 

I had system updates disabled in 5.16.5 by clearing the checkbox for updates 
in System Tray Settings -> General -> Extra Items but that checkbox is no 
longer there.

I had packagekit installed from previous trials so uninstalled it. Although I 
am no longer actively notified of system updates by Discover, 'Updates' still 
appears on the system tray Status and Notifications panel that appears when 
clicking on the system tray up-arrow and the tool tip shows System up to date, 
even when it is not.

The update notification comes from DiscoverNotifier but I haven't been able to 
see where such a service is activated, including in systemd.

Discover system updates is unusable in an Arch system. It suppresses pacman 
feedback and pollutes the pacman.log with countless [PACKAGEKIT] synchronizing 
package lists messages.

Is there a way to truly disable this service?

Regards,

Richard