I am really looking for a Radio-Clock for my iPhone. This seems to be non-trivial looking at iPhone/iPad alarm clock app with custom radio stream support . All proposed solutions require the app to be running until the alarm goes off. Now that we have Shortcuts this should be a piece of cake: start Alarm -> when done -> play my favourite radio url. Or is it not? Is there a reason in case it is not (besides Apple did not implemented it)?
I don't know about iOS devices, but if you have a HomePod, you could use the Home.app.
Home.app > Bottom of screen > Automation > Create Automation
Select "A Time of Day Occurs" > Time Of Day > Next
Select your HomePod > Next
Select When > Then Turn Off > set timer
Select Media > Choose Audio
This may help others.