Perhaps this addon does not require the appkey? Or what is the aim and benefit of this new addon? I am also interested in the motivation of this.
In the long term it would be interesting to have spotify integrated in LibreELECs/Kodis music interface, so that you can see the current track title and so on on your TV or connected GPIO LCD.
You don't need the appkey. It's working very well on OSMC, but I couldn't get it to work on LibreELEC.