The enqueue method in QtTextToSpeech import does not work with the Darwin tts engine on MacOS.

If you enqueue, say, 3 phrases "one", "two", "three" only the last one will be read. Furthermore, the "aboutToSynthesize()" signal will be emitted immediately three times, rather than when the next utterance in the queue is about to be read.

All the above does not apply to the "macos" engine, however it should be noted that the default engine selected at the initialisation of TTS is "darwin".

Perhaps, it would be beneficial for the default engine to be macos?