How can I move files by USB between a version 6.1 iPod Touch and a Linux machine?

I've recently dug out my old 5th Gen (A1421) model iPod Touch and put it back to factory settings. It's currently running version 6.1 (10B141) of its OS. I don't want to find that a software update has broken it one day, so my goal is to keep it offline as much as possible (specifically, Airplane Mode) and have it only talk to my PC, a Xubuntu 20.04 Linux machine. In line with this goal, I've never linked it up with any sort of iTunes software or Apple account. It was my hope that with the iPod set up as above, I would be able to connect it by USB to my PC and transfer files as I pleased. My goal is to use it to play mp3s. After all, Linux typically ignores whatever file system visibility restrictions that the connected device is trying to enforce. Now that I've tried that, my PC is only reporting that two devices exist: "iPod", contained only an empty DCIM folder, and "Documentes on iPod touch", containing nothing. When I try to move files to either of these, I either get an error message saying that a file doesn't exist or an error message saying that a directory doesn't exist. Unlocking the iPod does not change this, and the iPod does not seem to respond at all to anything that I'm doing on the PC, other than trying to charge its battery from my machine. So, given my goals, what can I do to be able to move files between the two devices? Could anything that I've done, such as putting the iPod in Airplane Mode, be to blame for my difficulties? I have managed to use ifuse to get new files on to the iPod , but the iPod itself shows no signs of recognizing them.