I believe there's a setting either in Discover (the KDE "app store") in the main plasma settings (somewhere in the "updates" section? That might be somewhere else, I don't remember) that will automatically install updates without you needing to approve them.

And there's also a setting that will wait to install them until the next boot. When I had that setting on, it only added maybe 10 seconds to my startup time when I needed to apply something like a kernel update.