All three applications appeared to work, but I did not see the expected warning message:

$ kcmshell5 kcm_kwin_effects
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/templates/OverlaySheet.qml:220:38: QML FocusScope: Binding loop detected for property "contentItemMaximumWidth"
kf.kirigami: Units.devicePixelRatio is deprecated (since 5.86 ): This returns 1 when using Qt HiDPI scaling.
QCoreApplication::postEvent: Unexpected null receiver
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/Page.qml:448: TypeError: Cannot read property 'globalToolBar' of null
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/AbstractApplicationItem.qml:94: TypeError: Cannot read property 'position' of null
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/AbstractApplicationItem.qml:93: TypeError: Cannot read property 'background' of null
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/newstuff/qml/Page.qml:155: TypeError: Cannot read property 'useLabel' of null
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/newstuff/qml/Dialog.qml:129: TypeError: Cannot read property 'uploadEnabled' of null
QCoreApplication::postEvent: Unexpected null receiver
kf.kirigami: Units.devicePixelRatio is deprecated (since 5.86 ): This returns 1 when using Qt HiDPI scaling.
kf.kirigami: Previous message repeats 71 times.
kio_http_cache_cleaner: Already running!
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/templates/OverlaySheet.qml:220:38: QML FocusScope: Binding loop detected for property "contentItemMaximumWidth"
kf.kirigami: Units.devicePixelRatio is deprecated (since 5.86 ): This returns 1 when using Qt HiDPI scaling.
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/Page.qml:448: TypeError: Cannot read property 'globalToolBar' of null
kf.kirigami: Units.devicePixelRatio is deprecated (since 5.86 ): This returns 1 when using Qt HiDPI scaling.
kf.kirigami: Previous message repeats 35 times.


$ kcmshell5 kwinscripts
kf.coreaddons: "Could not load plugin from "
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/templates/OverlaySheet.qml:220:38: QML FocusScope: Binding loop detected for property "contentItemMaximumWidth"
kf.kirigami: Units.devicePixelRatio is deprecated (since 5.86 ): This returns 1 when using Qt HiDPI scaling.
QCoreApplication::postEvent: Unexpected null receiver
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/AbstractApplicationItem.qml:94: TypeError: Cannot read property 'position' of null
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/AbstractApplicationItem.qml:93: TypeError: Cannot read property 'background' of null
mparillo@mparillo-virtual-machine:~$ kcmshell5 kwinscripts

$ kcmshell5 kwintabbox
kf.coreaddons: "Could not load plugin from "
load shortcut for  "Walk Through Windows"
load shortcut for  "Walk Through Windows (Reverse)"
load shortcut for  "Walk Through Windows of Current Application"
load shortcut for  "Walk Through Windows of Current Application (Reverse)"
load shortcut for  "Walk Through Windows Alternative"
load shortcut for  "Walk Through Windows Alternative (Reverse)"
load shortcut for  "Walk Through Windows of Current Application Alternative"
load shortcut for  "Walk Through Windows of Current Application Alternative (Reverse)"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/templates/OverlaySheet.qml:220:38: QML FocusScope: Binding loop detected for property "contentItemMaximumWidth"
kf.kirigami: Units.devicePixelRatio is deprecated (since 5.86 ): This returns 1 when using Qt HiDPI scaling.
QCoreApplication::postEvent: Unexpected null receiver
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/AbstractApplicationItem.qml:94: TypeError: Cannot read property 'position' of null
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/AbstractApplicationItem.qml:93: TypeError: Cannot read property 'background' of null