I just tried an example app with code from:
http://doc.qt.io/qt-5/qtqml-xmlhttprequest-get-qml.html
QNetworkManagerInterface::QNetworkManagerInterface(QObject*) propsReply "An AppArmor policy prevents this sender from sending this message to this recipient; type="method_call", sender=":1.107" (uid=32011 pid=7239 comm="/usr/lib/arm-linux-gnueabihf/qt5/bin/qmlscene $@ M") interface="org.freedesktop.DBus.Properties" member="GetAll" error name="(unset)" requested_reply="0" destination="org.freedesktop.NetworkManager" (uid=0 pid=1309 comm="NetworkManager ")"
QNetworkManagerInterface::QNetworkManagerInterface(QObject*) nmReply "An AppArmor policy prevents this sender from sending this message to this recipient; type="method_call", sender=":1.107" (uid=32011 pid=7239 comm="/usr/lib/arm-linux-gnueabihf/qt5/bin/qmlscene $@ M") interface="org.freedesktop.NetworkManager" member="GetDevices" error name="(unset)" requested_reply="0" destination="org.freedesktop.NetworkManager" (uid=0 pid=1309 comm="NetworkManager ")"
"Object path cannot be empty"
file:///opt/click.ubuntu.com/get.lorn-potter/0.1/Main.qml:61: TypeError: Cannot read property 'documentElement' of null
The calls GetAll and GetDevices are used in the QtBearer network manager backend.
This could be fixed by moving to using a QtBearer backend based on connectivity-api.
But I think that API is too sparse at the moment for a completely working QtBearer.