Librespot addon suddenly fails

Today, suddenly the Librespot addon fails on my CoreElec 21.2, Homatics Box. I can connect from my Spotify App, but it fails to play sound.
Strangely the Backend field in the Configuration was empty. So I choosed ALSA and tried several devices. But I am unsure, how exactly to create the device name from the aplay -l output.

Anybody else seeing this problem?