Found another command to recreate a plasma desktop via the console, so this is the output for a fully working desktop:
(I am guessing, there may be a widget making the original desktop not loadable?..)

filex@filex-ThinkPad-T530:~$ sudo plasmashell --replace
[sudo] password for filex: 
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
Checking screens: available: (QScreen(0x643043064570, name="LVDS-1")) redundant: QHash() fake: QSet() all: (QScreen(0x643043064570, name="LVDS-1"))
Checking screens: available: (QScreen(0x643043064570, name="LVDS-1")) redundant: QHash() fake: QSet() all: (QScreen(0x643043064570, name="LVDS-1"))
Aborting shell load: The activity manager daemon (kactivitymanagerd) is not running.
If this Plasma has been installed into a custom prefix, verify that its D-Bus services dir is known to the system for the daemon to be activatable.
QDBusConnection: name 'org.kde.kglobalaccel' had owner '' but we thought it was ':1.2'
Aborting shell load: The activity manager daemon (kactivitymanagerd) is not running.
If this Plasma has been installed into a custom prefix, verify that its D-Bus services dir is known to the system for the daemon to be activatable.
kf.plasma.quick: Applet preload policy set to 1
KTranscript: Loaded module: /usr/share/locale/ja/LC_SCRIPTS/ki18n5/ki18n5.js
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/templates/InlineMessage.qml:265:13: QML SelectableLabel: Binding loop detected for property "implicitWidth"
org.kde.plasma.libtaskmanager: Failed to determine whether virtual desktop navigation wrapping is enabled:  "The name org.kde.KWin was not provided by any .service files"
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
org.kde.plasma.containmentlayoutmanager: Error: cannot change the containment to AppletsLayout
QObject::connect: No such slot DesktopProtocol::_k_slotRedirection(KIO::Job *, QUrl)
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
Trying to use rootObject before initialization is completed, whilst using setInitializationDelayed. Forcing completion
org.kde.plasma.kicker: Entry is not valid "org.kde.kontact.desktop" QSharedPointer(0x643043ef5810)
org.kde.plasma.kicker: Entry is not valid "org.kde.kontact.desktop" QSharedPointer(0x643043ef6130)
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
Cyclic dependency detected between "file:///usr/share/plasma/plasmoids/org.kde.plasma.notifications/contents/ui/global/Globals.qml" and "file:///usr/share/plasma/plasmoids/org.kde.plasma.notifications/contents/ui/ThumbnailStrip.qml"
Cyclic dependency detected between "file:///usr/share/plasma/plasmoids/org.kde.plasma.notifications/contents/ui/global/Globals.qml" and "file:///usr/share/plasma/plasmoids/org.kde.plasma.notifications/contents/ui/NotificationHeader.qml"
org.kde.klipper: Failed to load history resource. Clipboard history cannot be read. :  History file does not exist
file:///usr/share/plasma/plasmoids/org.kde.kscreen/contents/ui/main.qml:30:5: Unable to assign [undefined] to bool
file:///usr/share/plasma/plasmoids/org.kde.plasma.networkmanagement/contents/ui/main.qml:95: TypeError: Cannot read property 'airplaneModeAvailable' of null
QFont::setPointSizeF: Point size <= 0 (0.000000), must be greater than 0
QObject::connect: No such slot DesktopProtocol::_k_slotRedirection(KIO::Job *, QUrl)
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/extras/PlaceholderMessage.qml:238:5: QML Heading: Binding loop detected for property "verticalAlignment"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/extras/PlaceholderMessage.qml:238:5: QML Heading: Binding loop detected for property "verticalAlignment"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/extras/PlaceholderMessage.qml:238:5: QML Heading: Binding loop detected for property "verticalAlignment"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/extras/PlaceholderMessage.qml:238:5: QML Heading: Binding loop detected for property "verticalAlignment"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/extras/PlaceholderMessage.qml:238:5: QML Heading: Binding loop detected for property "verticalAlignment"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/workspace/calendar/MonthView.qml:244:5: QML MonthViewHeader: Binding loop detected for property "implicitHeight"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/extras/PlaceholderMessage.qml:238:5: QML Heading: Binding loop detected for property "verticalAlignment"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/extras/PlaceholderMessage.qml:238:5: QML Heading: Binding loop detected for property "verticalAlignment"
file:///usr/share/plasma/plasmoids/org.kde.plasma.devicenotifier/contents/ui/DeviceItem.qml:36:5: Unable to assign [undefined] to bool
file:///usr/share/plasma/plasmoids/org.kde.plasma.devicenotifier/contents/ui/DeviceItem.qml:35:5: Unable to assign [undefined] to bool
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/extras/PlaceholderMessage.qml:238:5: QML Heading: Binding loop detected for property "verticalAlignment"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/extras/PlaceholderMessage.qml:238:5: QML Heading: Binding loop detected for property "verticalAlignment"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/extras/PlaceholderMessage.qml:238:5: QML Heading: Binding loop detected for property "verticalAlignment"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/extras/PlaceholderMessage.qml:238:5: QML Heading: Binding loop detected for property "verticalAlignment"
qt.svg: <input>:384:9: Could not resolve property: #linearGradient5187
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
KTranscript: Loaded module: /usr/share/locale/ja/LC_SCRIPTS/ki18n5/ki18n5.js
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/ScrollablePage.qml:200:9: QML MouseArea: Binding loop detected for property "width"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/ScrollablePage.qml:200:9: QML MouseArea: Binding loop detected for property "width"
QQmlEngine::setContextForObject(): Object already has a QQmlContext
QQmlEngine::setContextForObject(): Object already has a QQmlContext
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/Dialog.qml:335:9: QML ScrollView: Binding loop detected for property "calculatedImplicitWidth"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/templates/InlineMessage.qml:265:13: QML SelectableLabel: Binding loop detected for property "implicitWidth"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/templates/InlineMessage.qml:265:13: QML SelectableLabel: Binding loop detected for property "implicitWidth"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/templates/InlineMessage.qml:265:13: QML SelectableLabel: Binding loop detected for property "implicitWidth"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/templates/InlineMessage.qml:265:13: QML SelectableLabel: Binding loop detected for property "implicitWidth"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/templates/InlineMessage.qml:265:13: QML SelectableLabel: Binding loop detected for property "implicitWidth"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/ScrollablePage.qml:200:9: QML MouseArea: Binding loop detected for property "implicitHeight"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/ScrollablePage.qml:200:9: QML MouseArea: Binding loop detected for property "implicitHeight"
qml: The item SubCategoryPage_QMLTYPE_71(0x556c2fdc6230) is already in the PageRow
qml: The item SubCategoryPage_QMLTYPE_71(0x556c2fdc6230) is already in the PageRow
kf.configwidgets: A widget named "kcfg_AllowKDEAppsToRememberWindowPositions" was found but there is no setting named "AllowKDEAppsToRememberWindowPositions"
kf.configwidgets: A widget named "kcfg_ShadeHover" was found but there is no setting named "ShadeHover"
kf.configwidgets: A widget named "kcfg_ShadeHoverInterval" was found but there is no setting named "ShadeHoverInterval"
kf.configwidgets: A widget named "kcfg_Placement" was found but there is no setting named "Placement"
kf.configwidgets: A widget named "kcfg_HideUtilityWindowsForInactive" was found but there is no setting named "HideUtilityWindowsForInactive"
kf.configwidgets: A widget named "kcfg_ActivationDesktopPolicy" was found but there is no setting named "ActivationDesktopPolicy"
qml: The item SubCategoryPage_QMLTYPE_71(0x556c2fdc6230) is already in the PageRow
QQmlEngine::setContextForObject(): Object already has a QQmlContext
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/templates/InlineMessage.qml:265:13: QML SelectableLabel: Binding loop detected for property "implicitWidth"
file:///usr/share/kpackage/kcms/kcm_workspace/contents/ui/main.qml:46:5: QML FormLayout (parent or ancestor of QQuickLayoutAttached): Binding loop detected for property "preferredHeight"
file:///usr/share/kpackage/kcms/kcm_workspace/contents/ui/main.qml:46:5: QML FormLayout (parent or ancestor of QQuickLayoutAttached): Binding loop detected for property "preferredHeight"
file:///usr/share/kpackage/kcms/kcm_workspace/contents/ui/main.qml:46:5: QML FormLayout (parent or ancestor of QQuickLayoutAttached): Binding loop detected for property "preferredHeight"
qml: The item SubCategoryPage_QMLTYPE_71(0x556c2fdc6230) is already in the PageRow
qml: The item SubCategoryPage_QMLTYPE_71(0x556c2fdc6230) is already in the PageRow
QQmlEngine::setContextForObject(): Object already has a QQmlContext
qml: The item SubCategoryPage_QMLTYPE_71(0x556c2fdc6230) is already in the PageRow
qml: The item SubCategoryPage_QMLTYPE_71(0x556c2fdc6230) is already in the PageRow
QQmlEngine::setContextForObject(): Object already has a QQmlContext
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/templates/InlineMessage.qml:265:13: QML SelectableLabel: Binding loop detected for property "implicitWidth"
file:///usr/share/kpackage/kcms/kcm_workspace/contents/ui/main.qml:46:5: QML FormLayout (parent or ancestor of QQuickLayoutAttached): Binding loop detected for property "preferredHeight"
file:///usr/share/kpackage/kcms/kcm_workspace/contents/ui/main.qml:46:5: QML FormLayout (parent or ancestor of QQuickLayoutAttached): Binding loop detected for property "preferredHeight"
file:///usr/share/kpackage/kcms/kcm_workspace/contents/ui/main.qml:46:5: QML FormLayout (parent or ancestor of QQuickLayoutAttached): Binding loop detected for property "preferredHeight"
qml: The item SubCategoryPage_QMLTYPE_71(0x556c2fdc6230) is already in the PageRow
QQmlEngine::setContextForObject(): Object already has a QQmlContext
qml: The item SubCategoryPage_QMLTYPE_71(0x556c2fdc6230) is already in the PageRow
QQmlEngine::setContextForObject(): Object already has a QQmlContext
^C
filex@filex-ThinkPad-T530:~$ sudo plasmashell --replace
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
Checking screens: available: (QScreen(0x621245febae0, name="LVDS-1")) redundant: QHash() fake: QSet() all: (QScreen(0x621245febae0, name="LVDS-1"))
Checking screens: available: (QScreen(0x621245febae0, name="LVDS-1")) redundant: QHash() fake: QSet() all: (QScreen(0x621245febae0, name="LVDS-1"))
Aborting shell load: The activity manager daemon (kactivitymanagerd) is not running.
If this Plasma has been installed into a custom prefix, verify that its D-Bus services dir is known to the system for the daemon to be activatable.
QDBusConnection: name 'org.kde.kglobalaccel' had owner '' but we thought it was ':1.2'
Aborting shell load: The activity manager daemon (kactivitymanagerd) is not running.
If this Plasma has been installed into a custom prefix, verify that its D-Bus services dir is known to the system for the daemon to be activatable.
kf.plasma.quick: Applet preload policy set to 1
KTranscript: Loaded module: /usr/share/locale/ja/LC_SCRIPTS/ki18n5/ki18n5.js
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/templates/InlineMessage.qml:265:13: QML SelectableLabel: Binding loop detected for property "implicitWidth"
org.kde.plasma.libtaskmanager: Failed to determine whether virtual desktop navigation wrapping is enabled:  "The name org.kde.KWin was not provided by any .service files"
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
org.kde.plasma.containmentlayoutmanager: Error: cannot change the containment to AppletsLayout
QObject::connect: No such slot DesktopProtocol::_k_slotRedirection(KIO::Job *, QUrl)
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
Trying to use rootObject before initialization is completed, whilst using setInitializationDelayed. Forcing completion
org.kde.plasma.kicker: Entry is not valid "org.kde.kontact.desktop" QSharedPointer(0x621246ea0990)
org.kde.plasma.kicker: Entry is not valid "org.kde.kontact.desktop" QSharedPointer(0x621246ea12b0)
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
Cyclic dependency detected between "file:///usr/share/plasma/plasmoids/org.kde.plasma.notifications/contents/ui/global/Globals.qml" and "file:///usr/share/plasma/plasmoids/org.kde.plasma.notifications/contents/ui/NotificationHeader.qml"
Cyclic dependency detected between "file:///usr/share/plasma/plasmoids/org.kde.plasma.notifications/contents/ui/global/Globals.qml" and "file:///usr/share/plasma/plasmoids/org.kde.plasma.notifications/contents/ui/ThumbnailStrip.qml"
org.kde.klipper: Failed to load history resource. Clipboard history cannot be read. :  History file does not exist
file:///usr/share/plasma/plasmoids/org.kde.kscreen/contents/ui/main.qml:30:5: Unable to assign [undefined] to bool
file:///usr/share/plasma/plasmoids/org.kde.plasma.networkmanagement/contents/ui/main.qml:95: TypeError: Cannot read property 'airplaneModeAvailable' of null
QFont::setPointSizeF: Point size <= 0 (0.000000), must be greater than 0
QObject::connect: No such slot DesktopProtocol::_k_slotRedirection(KIO::Job *, QUrl)
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/extras/PlaceholderMessage.qml:238:5: QML Heading: Binding loop detected for property "verticalAlignment"
file:///usr/share/plasma/plasmoids/org.kde.plasma.devicenotifier/contents/ui/DeviceItem.qml:36:5: Unable to assign [undefined] to bool
file:///usr/share/plasma/plasmoids/org.kde.plasma.devicenotifier/contents/ui/DeviceItem.qml:35:5: Unable to assign [undefined] to bool
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/extras/PlaceholderMessage.qml:238:5: QML Heading: Binding loop detected for property "verticalAlignment"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/extras/PlaceholderMessage.qml:238:5: QML Heading: Binding loop detected for property "verticalAlignment"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/extras/PlaceholderMessage.qml:238:5: QML Heading: Binding loop detected for property "verticalAlignment"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/workspace/calendar/MonthView.qml:244:5: QML MonthViewHeader: Binding loop detected for property "implicitHeight"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/extras/PlaceholderMessage.qml:238:5: QML Heading: Binding loop detected for property "verticalAlignment"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/extras/PlaceholderMessage.qml:238:5: QML Heading: Binding loop detected for property "verticalAlignment"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/extras/PlaceholderMessage.qml:238:5: QML Heading: Binding loop detected for property "verticalAlignment"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/extras/PlaceholderMessage.qml:238:5: QML Heading: Binding loop detected for property "verticalAlignment"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/extras/PlaceholderMessage.qml:238:5: QML Heading: Binding loop detected for property "verticalAlignment"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/extras/PlaceholderMessage.qml:238:5: QML Heading: Binding loop detected for property "verticalAlignment"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/extras/PlaceholderMessage.qml:238:5: QML Heading: Binding loop detected for property "verticalAlignment"