var u=new SpeechSynthesisUtterance() gives a speech synthesis object,
u.text="Hello, world!" gives something to say,
but speechSynthesis.speak(u) doesn't work.
welcome to the forum.
Android's WebView instance does not support speech synthesis.
But the Crome Browser on Android does.
You can use the Basic's TTS-Commands parrallel to the HTML-Commands.
Look at the f37_html_demo.bas program for your first steps.