After double click on qt-opensource-mac-x86-5.13.2.app to open it. A dialog appears saying: "Verifying "qt-open..."
After 5 minutes is stops with the message, "The application could not be started because Apple was not able to check ...."
this is a notarization problem
After the ~10th try to open the application it works - at least on one machine, others still not open the installer