Can you just plug a USB jump drive with FLAC and WAV files into the USB port on the bridge and play them? I understand about the network hookup (ethernet) to control the playback, but what is the USB input for if not to take Jump drives or external USB hard drives?
No, The bridge does not support playing from USB. It is used for emergency rescue.
To enable playback of a music library residing on your memory stick/USB disc, the Bridge need to contain an uPnP server to enable media browsing.
There are devices that compete with Bridge (same price region) that can do this.
I see that you can add shares to the Linux box - this will help