I didn’t have time to the debug log. But I’ve replaced the USB dongle with another one. I Guess that the older one, wasn’t a 100 mbit one as stated on aliexpress. With the new one the loading of spotify playlists goes a bit faster. Only 5 minutes on my Pi Zero. Which takes only half a minute on a pi 3. The 5 minutes is okay with me.
It would however be very nice of initializing the Spotify playlist could take place in the background, so that I can use mopiyd for my local mp3 files until the playlists are fully loaded.
edited: I’ve also discovered that I have a slow sd card 400x and ordered a 600x speed. Hope it helps. Will keep you informed.