Have been looking for this since I heard Soundrop was shutting down:

On November 13th 2014, popular music sharing service Soundrop announced it would be closing its doors. With no suitable alternative available, I set out to build an open-source replacement. I wanted to harness Spotify’s excellent audio quality and music library, but since they are shutting down all Spotify Apps, the only viable option was to build a stand-alone player. A month of late nights later, and the first version of Soundbounce is now ready to download.

http://soundbounce.org/

Linux support is growing, the app runs but there are issues with audio playing and installation.

If you are interested find the details here: https://github.com/pdaddyo/soundbounce/issues/114

edit: I’ve just put a $50 bounty on someone making an Ubuntu compatible .deb for me :D