The discover notification icon does not work to install updates.
When you right click on it, a menu is opened with the option to install the updates. When you click on it to install the updates, nothing happens. There is just a change in the icon, but the updates are not installed.
Is this an upstream bug?
Opensuse had an excellent updater notifier, it’s sad it’s gone.
I’ve opened a bug in KDE bugzilla and was informed that plasma 6.4.2 is no longer maintained, so no fix from kde.
Since Leap should be a more stable system, isn’t it wise to bring back the opensuse notification applet while discover is still so buggy?
And let discover deal only with it was designed for, just to be a app store 
Consider upgrading the Plasma desktop environment as shown here:
Don’t know if using “bleeding edge” versions are a good choice when you are looking for stability and funcionality. But I will give it a try in a non production machine.
Well you need to evaluate this for yourself (no such thing as a perfect world). FWIW, I use both Slowroll and Leap, and I’ve always used the current KDE Plasma version with Leap installs. Very few issues encountered, but I’m an experienced user with no specialized software needs, and most often using machines with Intel graphics.