Server Version#: 1.25.9.5721
Player Version#: 4.2.0
In recent versions of Plexamp on Linux, currently playing music no longer appears in KDE’s media player. I believe this uses MPRIS, so I suspect this integration is broken with other desktop environments too, e.g. Gnome. Interestingly, KDE Connect will show Plexamp as a multimedia control source, with completely working playback controls, album art, etc.
This worked a few months ago, and I suspect the regression occurred in either 4.1.0 or 4.0.0.