Plasmashell High CPU Load Fix - Plasma 5.15 KDE on Kubuntu 19.04

Editing the /usr/share/plasma/plasmoids/org.kde.plasma.notifications/contents/ui/NotificationIcon.qml file seems to do the trick (your mileage may vary). Look for this section:

PlasmaComponents.BusyIndicator {
    anchors.fill: parent 

    visible: jobs ? jobs.count > 0 : false
    running: visible
}

..and change it to read:

 PlasmaComponents.BusyIndicator {
    anchors.fill: parent

    visible: jobs ? jobs.count > 0 : false
    running: false
}

Essentially, just replacing the "visible" with "false"

• Restart/reboot, and it may work fine.

I have a Kubuntu 21.10,

KDE Frameworks Version: 5.86.0
Qt Version: 5.15.2
Kernel Version: 5.13.0-25-generic (64-bit)
Graphics Platform: X11

And I have problems with Plasmashell High CPU when invoke Klipper history list.

And this helps me:
KDE plasmashell stuck in 100% cpu because of large JSON in the clipboard https://blog.inticol.com/2020/04/kde-plasmashell-stuck-in-100-cpu.html

Just clean clipboard history