The height of the Item in the ListView is not reflected in the contentHeight when there is only one Item.

ListView {
    id: listView
    visible: notificationDeviceManager.deviceIdList.length !== 0
    anchors.horizontalCenter: parent.horizontalCenter
    width: useNameArea.width // Width of the sibling
    height: contentHeight
    spacing: 10
    model: notificationDeviceManager.deviceIdList
    interactive: false   
 
     property int cellHeight: bodyArea.height * 0.1 // Height of the parent    
     delegate: Item {
        width: listView.width
        height: listView.cellHeight
    }
}

ListView {
...
    onContentHeightChanged: {
        console.log("onContentHeightChanged : contentHeight : ",  contentHeight);
    }

    onHeightChanged: {
        console.log("onHeightChanged : height : ", height);
    }
...
}