I have Plasma set to Update Automatically and to Apply System Updates After Rebooting.

I does notify me that there are new updates, but it never does anything else with it.

I was expecting, once the notification is shown, it would download the updates in the background and offer to install them at shutdown.

But that never happens unless i manually open Discover and press the "Install All" button (which, basically, kills the whole idea of "automatic")