Qt Creator takes unreasonably long to start up

When the Creator is started it hangs on the startup screen (image attached) for over 5 minutes. I already described part of this in the thread https://qt-project.org/forums/viewthread/32179 and in bug https://bugreports.qt-project.org/browse/QTBUG-34657

This behavior only occurs for non priviledged users on the Qt Creator installed with the Libary (in Qt/Tools/qtcreator) not with the one installed standalone.

It might be related to network mapped home drives (that contain the appdata folder and thereby the settingspath).
However, even with the settingspath being set to a local folder (C:\temp) I had to abort the startup after 5 minutes of unresponsiveness.

The taskmanager shows that the qtcreator.exe reads ~100bytes/s (in one read) during this unresponsive time.