OK: ended up with a Schiit Modi+ (had the necessary specs). Signed up for Amazon Ultra HD music. App runs on my iPhone: can hear music on iPhone speakers. When I connect the iPhone (lightening connector) to the Modi+ (USB C connector) I get nothing downstream to amp/speakers. In Amazon app, there is a screen that looks like it should be showing the Modi+ as a possible output target, but it does not appear there. Tried multiple cable configurations and at least two iPhones and one Apple MacBook Air: no dice;
Any thoughts?