Yeah it is recognized as RM-821|Nokia Lumia 920 device.
And mp3's stay there but Music app doesn't play them or find them. I copy files to Music/Albums, Music/Artust and Music/Playlist folders. I tried with lot of different mp3s. Still none of them found when I open Music app.
This is really mystery. So the Music app should find your mp3s from the phones Music folder automatically? Is there any other music player for WP than default?
i have both Samsung focus S & Lumia 920, i was able to sync music (Specific play list) to Focus S using rythombox (Ubuntu 12.10), it didn't sync the artist information but was able to play songs on focus s, still trying to sync Lumia 920 no luck so far. Ubuntu doesn't even mount my Lumia 920, will let you know if i am successful.
Basically, the only way I have been able to do it for now is to use a windows computer to copy the files from the phone onto Win and back to phone..... not the best, but at least I am able to use the phone as a storage device from my Ubuntu comp....
When I was using Ubuntu as my primary OS and using an iPhone, I had to create a VirtualBox VM running Windows XP so I could use iTunes for phone management (including music syncing, since it was never smooth on Linux). You might want to consider something like that... you could map your Linux music folders onto your Windows VM through the VirtualBox software, and copy them from Windows using the VirtualBox USB mapping.
Otherwise, I think you're SOL unless Ubuntu handles MTP... which it may do in theory, but putting it into practice is something different altogether.
I also have considered this, I have been trying to find a way to modify the Syncing app with a program like Orca, but needs a MSI application and not exe. The app sees Wine and PlayonLinux as a server OS and I remember doing something similar to this to get Zune to work on Server 2008+R2 for my Windows 7 handset. If that doesn't work then a VM machine is the only way.