It was very promising before the last update of Survey 123. I tested Understanding Survey123's custom URL Scheme and was able to send data, open and populate fields in a survey.
In the last update you made a function that downloads the survey but it makes it all stop to work. My URL is:
arcgis-survey123://?itemID=59321a93d2bc416a83dceca1607bca65 (This URL doesn´t populate a field- but I simplified it in order for a higher success rate)
Look at this video so you understand what I am talking about. https://youtu.be/p9byN7gGu4A
The device is an Ipad mini 4, iOS 10.0.2, Latest release of Collector and Survey123