In summary, Spotify was working on integrating their latest desktop versions into Linux, and then just stopped about 6 months ago. Then yesterday, they pushed it live anyway and revealed that no one is working on Linux, but maybe someday they'll get around to it.

"The intention was to fix a few of the bigger issues and then quickly move this to stable. That never happened, since after September, we have had no developers working on the linux client. There are still lots of problem with this version of the client for linux, but we are now seeing much more problems with the old client."