/usr/share/plasma/plasmoids/org.kde.plasma.systemloadviewer/ is in plasma-widgets-addons 4:5.5.5-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/plasma/plasmoids/org.kde.plasma.systemloadviewer/contents/
/usr/share/plasma/plasmoids/org.kde.plasma.systemloadviewer/contents/config/
/usr/share/plasma/plasmoids/org.kde.plasma.systemloadviewer/contents/config/config.qml
/usr/share/plasma/plasmoids/org.kde.plasma.systemloadviewer/contents/config/main.xml
/usr/share/plasma/plasmoids/org.kde.plasma.systemloadviewer/contents/ui/
/usr/share/plasma/plasmoids/org.kde.plasma.systemloadviewer/contents/ui/BarMonitor.qml
/usr/share/plasma/plasmoids/org.kde.plasma.systemloadviewer/contents/ui/CircularMonitor.qml
/usr/share/plasma/plasmoids/org.kde.plasma.systemloadviewer/contents/ui/ColorPicker.qml
/usr/share/plasma/plasmoids/org.kde.plasma.systemloadviewer/contents/ui/ColorSettings.qml
/usr/share/plasma/plasmoids/org.kde.plasma.systemloadviewer/contents/ui/CompactBarMonitor.qml
/usr/share/plasma/plasmoids/org.kde.plasma.systemloadviewer/contents/ui/ConditionallyLoadedMonitors.qml
/usr/share/plasma/plasmoids/org.kde.plasma.systemloadviewer/contents/ui/ConditionallyRoundedRectangle.qml
/usr/share/plasma/plasmoids/org.kde.plasma.systemloadviewer/contents/ui/GeneralSettings.qml
/usr/share/plasma/plasmoids/org.kde.plasma.systemloadviewer/contents/ui/SystemLoadViewer.qml
/usr/share/plasma/plasmoids/org.kde.plasma.systemloadviewer/metadata.desktop