I'm not sure what I was expecting here, maybe iPods to be a solved problem, but it seems music players are in a pretty poor state right now. Maybe that's unsurprising given Spotify and Apple Music, but I was hoping for more.
All I want, ideally, is something that will parse music on my NAS, and pipe it over to the iPod. On Windows, having tried everything from Winamp on, Foobar's by far the best. It easily handles a large library on a NAS, but the iPod sync leaves a lot to be desired.
On Kubuntu, I'm struggling to find anything that will parse a large remote library. Well, that's not true, MOC is fine, but the graphical apps are all dying, and/or super duper slow. Meh.
So I've put Rockbox on the iPod. That'll let me copy music from the desktop, sidestepping the middle man. Early days atm, but playing .flac on the iPod is a nice win.