Hello, you can only use predefined sounds as an alarm clock, i.e. neither radio nor Spotify playlist.

At first I thought I was annoyed that "Create a radio alarm clock with Radio Argovia" was ignored just as skilfully as the procedures, which I only found with difficulty at all in the Home > Assistant settings thanks to the search.
After a little research, however, I reached my goal: in the Google Home app (which was/is also used to set up the Smart Clock) in the Assistant settings, simply change the language from German (Switzerland) to German (Germany). That makes the difference. Now it dutifully carries out the "Good morning" procedure after the alarm clock has stopped ringing (e.g. announcing the weather, opening the SmartHome blinds and playing Radio Argovia), which it refused to do before, except for the weather. Also, the instruction mentioned at the beginning to create a radio alarm clock instead of a standard alarm clock with ringtone now works. So yes, it can also be a radio alarm clock - with a little help.