The process for classic confinement review is well documented in Process for reviewing classic confinement snaps - access to org.freedesktop.DBus.ListNames is not one of the known categories for classic confinement.
You should be able to enumerate players by plugging both the desktop-legacy interface (to give access to the session bus) and system-observe to allow to run ListNames.
I am not sure about mpris control though at this point - that will need more investigation.