What is the difference between discovery url and endpoint url for opc serves?
Discovery URL contains the initial host/port we'll contact to call the discovery services, including the GetEndpoints service.
The endpoint we actually want to connect to may have a different URL than the discovery URL, so it's separately configurable.
For many servers these will be the same. For Ignition they will be different.
This is an advanced view that you should only need to deal with if the server is offline and you already know exactly the configuration details of that server.