By the way I am using Unity 2019.2.3f1 if that matters.
I created a new project and imported the latest from the Unity Asset store. I then deleted the files in the iOS folder and put the 206.a file there.
I built it for ios and ran it. It runs fine without crashing and shows the web page. When I hit the button to ping unity it gives errors, but they are probably because I didn’t change any of the default code.
Since this works I will try to figure out what is different.
One thing: your example waits for the user to press a button before loading the web component and showing the web page. I do it on startup because my whole app is web based. Could that have something to do with the issues? Do I have to wait for something to initialize first? Can you do some testing on that?