This has been beaten to death in the main Ambient Mode thread.
Bottom line: iOS support for Ambient Mode in
SmartStupidThings is crippleware at best; vaporware at worst. Samsung CS says to call StupidThings CS; StupidThings CS admitted that their iOS version doesn’t actually support uploading or other purported features of Ambient Mode. (Since the original posts, there apparently have been some updates to the iOS version of StupidThings, but they still don’t seem to have the bugs worked out.)
Only way I could ever do much of anything close to what Samsung promises for Ambient Mode was to use a friend’s Android device (and no small amount of kludging/hacking/experimenting). Especially for 2017-18 models, Ambient Mode is pretty much a fraud, so don’t be surprised if you can’t get your expensive new 2019 TV to do what Samsung advertises it can.
And, unfortunately, don’t expect any help from Samsung here — while the Moderators in this forum are generally quite good (miles better than their US counterparts!), I suspect that the reason they aren’t chiming in on any of the Ambient Mode discussions is that Samsung can’t or won’t give them any accurate info on Ambient Mode’s shortcomings.