I've got one of those dual drives - opens one side to be USB-C and opens the other side to be USB-A. My concern though is leaving it in the USB-C and knocking it when putting things down in the cubby hole so now I have USB-C to USB female small cable that I poke through the hole.I just bought a USB-C drive and put movies/music on there. Doesn't seem to be anything internal anymore.
I use one of those tiny USB drives that really only sticks out a quarter of an inch if even that. I actually prefer the USB route over internal memory storage as it is much easier to just prepare the USB drive. Since the E-tron can read playlists on the USB drive, using very large drives with lots of music is pretty managable.There are angled USB-C adapters that can be then tucked away for safer keeping. I still prefer SD card reader - equally fast and the card slots in and it is safe.