QAbstractNativeEventFilter won't receive event when QT_QML_DEBUG is defined and the QApplication is started from a thread
My understanding is that using QT_QML_DEBUG will run some static code upon initialization (it instantiate a QQmlDebuggingEnabler), this will create some Thread Local Storage data (when using QDebug) so the thread of the "main()" will be considered as the main thread. Later on, when registering a QAbstractNativeEventFilter, it will be registered in the TLS of this thread, whereas the native events are sent to the thread of the QApplication
I attached a sample to reproduce the issue.
The problem doesn't seems to occurs in newer version (I tested it with 5.12.8 and 5.15.1)
I don't know if I can expect this bug to be fixed as 5.11 is not an LTS version.