Since I can't reproduce the failing tests locally, I try to guess and pass -platform minimal to these tests since they have in common to use QCoreApplication resp. QApplication and at least one of the tests spit out a few warnings locally about being unable to register a certain Qt-internal window, which is related to having a full platform available, which is not the case on our CI clients. We already did it in the past with Qt 5 on Linux for a few tests.