As this thread is now obsolete, and to avoid confusion I will now lock this thread.
If you are looking for a Spotify client for Ubuntu Touch, you can check out this thread:
https://forums.ubports.com/topic/4346/futify-spotify-client-need-beta-testers

It is already in a good state, but it will be available in the Open Store when the copyrights issue will be solved.

Thanks @manland for your very appreciated contribution.