Great list! Not sure how I've missed all these in my search but I've had success with Plexamp (Gnome, Fedora), with Plex served from my Synology NAS. Opinions on Plex aside, it's been the most successful "native" experience across mobile/linux that just works.

Majority of GTK/Adwaita solutions are always so close but missing something critical, especially when using DLNA (e.g treated as secondary to local library, intermittent first load issues etc) That said, I got quite far with Gapless [1]

1. https://gitlab.gnome.org/neithern/g4music