AVSpeechSynthesizer seems to support english with multi delegates (britsh, us...)
Does it support other languages? french, Portuguese ... is there a list of these languages somewhere ?
Yes, it does. Use speechVoices of AVSpeechSynthesisVoice to get a list of available voices with supported languages.
let voices = AVSpeechSynthesisVoice.speechVoices() //list of supported voices
print(voices[0].language) //print first voice locale
Currently (as of 10 September 2018, on iOS 10.3.1 and 11.4.1) you'll find these: