Qt.labs.platform version version number in Buster?

[Jürgen Bausa <Juergen.Bausa@online.de>]

I try to run the buster backport of ausweisapp2. Although I can start the 
program the gui does not pop up. Instead I get the following message:

qrc:/qml/main.qml:31 module "Qt.labs.platform" version 1.1 is not installed

As qml-module-qt-labs-platform is installed, I think it doesnt have the 
correct version number. However, I cant find the version number of the debian 
package (obviously this is different to the qt-version number whcih is 5.11.3). 
Is there any way to get this information?

Juergen