That depends on what URL you specified, because it’s specific to your server. If in doubt, delete the URL from your settings to Autodiscover your OH server.
And if you haven’t turned on API Security in openHAB 3’s settings, make sure to delete your user/password from the app.
the app does not find anything. It just shows this symbol for searching - but it does not find anything.
My settings under API Security are as follows:
Your settings are correct, so it shouldn’t be a problem there. Assuming your OH server and phone are on the same network, it’s strange that the app can’t find the server through autodiscovery.
The URL in the app can be either the IP address or host name of your openHAB server, which is the same as what you use to access the dashboard through a web browser. So, your Local Server settings should be: