I downloaded Google-music-manager from here : https://play.google.com/music/listen#/manager.
Installing with gdebi showed the following :
Error : Dependency is not satisfiable : libc6 ( >=2.15 ).......
After some Googling I found an older version from this link ( google music )
Installed without trouble...
To have it work properly ( the "Upload" menu item missing and the "Options" item not doing anything ) I had to delete the ~/.config/google-musicmanager directory and start the manager again ( link ).
Additional link for download ( version 188.8.131.5218-r0 ) : here. ( google-musicmanager-beta_current_amd64.deb ).