I just picked up an S5 and noted that it has issues displaying the webcam in applications. It fails to load in either Cura (3.4.1, 3.5 and 3.5.1) or the Ultimaker iPhone app. I have tested with the URL as well.  Using the /?action=stream it will try to initiate a download in Edge (Win10) and works fine in Chrome.  Using the /?action=snapshot works in both browsers.  I have tried this on multiple PC's/phones as well. My UM3 does work fine through the same applications.