Apparently it seems it's not possible to control spotify via dbus.
An example of application where this is causing problems is KDE connect, an android app that allows to control many multimedia applications under linux. Due to the incomplete dbus support of spotify this cannot be done just for spotify.
Solved! Go to Solution.
Nobody is working on it currently, but it is tracked internally as "Add more MPRIS functionality", that I want to do eventually. There are some linux crash bugs that I want to focus on first. I can set aside one day every two weeks to help fixing bugs in the linux system specific parts of the desktop client. That is roughly the pace of development currently.
The easy stuff like raise/quit, position, volume is in the list of things to build, as well as better coverart support which is trickier to build.