Hi Richard,
I believe the reason it only works in the browser is because the javascript action leverages a HTML5 function:
window.speechSynthesis.speak(utterance);
The library it is using is only available when using web technology, so it’ll work in hybrid and responsive mode but not Native: https://developer.mozilla.org/en-US/docs/Web/API/SpeechSynthesis.
You’d have to use a different React Native library to achieve the same functionality. Something like this:
https://www.npmjs.com/package/react-native-tts
I hope this helps? I agree the documentation should have a warning. If you submit a feedback, i’m sure someone will pick it up and change it for you.
Regards
Simon