Hey there, flemmig and grigrizljac
I managed to fix the issue with the sound in iOS,
In my case it was the WKwebview - do not check that box when exporting the game from Construct,
Also do not use that plugin in Intel xdk // I removed those 2 things and the game had audio.
However, the audio was distorted.
I googled it the issue and apparently iOS 9 uses 48KHZ frecuency in the audio, so what I did was converting the audio files to that frecuency using this website:
Now my game has audio and in good quality,
I am still facing one last issue - when I plug the headphones and then unplug them the audio gets a bit distorted. I am still trying to solve that issue out,
I hope this reply help you guys,