The following file is installed by plasma-mediacenter, as well as kdeplasma-addons: share/kde4/services/plasma-applet-mediaplayer.desktop This makes it impossible to install both packages with some package manager systems.
As of the following commit, Plasma Media Center no longer uses plasma-applets but only plasma QML components- https://projects.kde.org/projects/playground/multimedia/plasma-mediacenter/repository/revisions/0e6e471dfec8424565e3b42d2023ed6707a8aa83 So, PMC will no longer install any applets, and this bug can be closed as fixed :)
Thanks for the update, the issue is fixed. Would it make sense to just "git rm" the "old" directory, or is it's content needed for further refactoring to QML?
Yes, it might be needed for some more time. Is there any problem if it's there?