Currently, the problem is that Qt Safe Renderer does not work in QtCreator designer without building QSR from the sources and rebuilding the QML puppet. From the end-user point of view this is quite cumbersome and rebuilding QML Puppet is an unstable feature.
I have tested manually in Windows by extracting the following zip:
From that zip file SafeRenderer (from qml/Qt) folder, subfolders and files should be copied to the QtCreator binary folder: Tools\QtCreator\bin\qml\Qt
Then designer works flawlessly without rebuilding the puppet (and using the default Fallback QML emulation layer setting).
Similarly, we should add Linux and Mac dynamically build libraries to the ci-files and add those to the installer.