Docker configuration might be the problem.
Port 1900 has to be open for SSDP in order to discover devices.
Hmm, very unlikely, because in my case MC is not running in a docker container.
And I have to add: This problem only occurs with JRemote under iOS. With JRemote 2 and Gizmo (under Android) "this device" is offered in the same environment.
And I remember another user couple of years ago mentioning a similar problem that he solved by adding a zone (no zone at all before).
I believe there is a problem with the iOS JRemote code that runs into trouble once there is no streaming device available in the environment. To me it sounds like a bad or wrong termination condition in the first loop run while it faces no item. I assume the code should be similar like follows:
1. Start loop
2. Find device
3. Exit loop when no device found
4. Add "this device"
If there is an error occuring within the loop and this error isn't catched properly then step 4 might not be executed.
Just an idea....