MikeMc

It sounds to me like the app isn't getting SSDP replies from the controller -- or perhaps that your iOS devices are using WiFi Assist (which uses LTE when iOS thinks the WiFi isn't great).  Without 4Sight any connections that employ WiFi Assist would be problematic.  Same deal for camera connections.  You can check if WiFi assist is enabled and / or turn it off:
https://www.imore.com/how-to-turn-off-wifi-assist-ios-iphone
and see if that makes a difference.

It sounds to me like the app isn't getting SSDP replies from the controller -- or perhaps that your iOS devices are using WiFi Assist (which uses LTE when iOS thinks the WiFi isn't great).  Without 4Sight any connections that employ WiFi Assist would be problematic.  Same deal for camera connections.  You can check if WiFi assist is enabled and / or turn it off:
https://www.imore.com/how-to-turn-off-wifi-assist-ios-iphone
and see if that makes a difference.

This is indeed an Apple bug.  If you shake your device (really), the TouchID alert will show up.

There's a bug in iOS 13 that's causing this behavior.  It will be fixed in iOS 13.1 which is set to be released September 24th.  (You can beta 13.1 now if you're so inclined!)

How badly do you want something like this to work?  You might be able to set up a proxy / tunnel on something like a Raspberry Pi, have it listen on a single IP to any number of ports and then forward the traffic on to separate IP addresses / ports as needed.  (This is all internal to your network of course.)
caveat emptor -- I've not tried this, it requires work beyond a driver and it might be a headache to maintain.  

My suspicion would be that the iOS app is asking the driver for a thumbnail resolution of a given size (with a 16:9 aspect ratio if the driver states that it's supported) and then provides a URL that the camera can't actually fulfill.  Try setting the aspect ratio for the camera to 4:3 in Composer and see if that fixes your thumbnails on iOS.