Suggestions for the future: Headless RPi support!
So, this was a pleasant surprise! Plexamp is exactly what I would expect out of a modern, Plex-based dedicated music player, and for a first release of a "passion project", it blew me away. That said, of course there are some bugs and issues, but I'm sure you're already working on most of that.
What struck me the most, however, was how perfectly this integrated in what I have been trying to build at home, but haven't really been able to: a simple, efficient, Raspberry Pi-based client music player for network stored music.
Current setup: A single Raspberry Pi running Volumio, a MPD-based linux dist and client/server application that can be remote controlled by any standard MPD remote, or the specific Volumio remote client on iOS.
My dream setup: Plexamp running as a stand-alone app on the same Raspberry, presumably under some kind of separate light-weight Linux dist or as its own image, with a corresponding Plexamp app on iOS (along with the macOS and Windows apps of course).
So, the RPi Plexamp application (the "client") would be running headlessly and outputting to my HiFiBerry DAC, connected to a headphone amp. It would be streaming the music from Plex Media Server (the "server"), or any other compatible source I choose. I would control the "client" using a Plexamp iOS app (the "remote"), which of course would in itself be the full client/server application, in case I want to listen directly from my phone.
Presto! Perfect headless playback from a dedicated HiFi player setup, with support for gapless, ReplayGain, all the goodies, controlled by a beautiful and rich remote and streaming everything from my central, carefully managed Plex Media Server library. Doesn't that sound just great? I know it does to me
The best thing about this is that it's basically halfway there already. As far as I can tell, all the APIs and blocks you're using already have full linux support, meaning there's no reason whatsoever there should be any issue porting it. The backend already supports the client/server/remote control framework. The only thing left would be the iOS-compatible version (and, of course, we can't forget our Android-loving friends as well) of the app, but again, since most of this is "web"-tech to begin with, there should be plenty of ways to port this over, even if it's not as a truly native iOS application.
I'd love to hear comments from someone in the Plex team, as well as from anyone else who'd be interested in the same kind of setup.