If the QR code is able to be output to the internet by the Pi, doesn't the Pi have to have an internet connection? Such connection would entail other data transferred to and from the Pi, if I'm not mistaken. While there would be an airgap between the source of the QR code and the Pi, since no other connection to it, nor to the internet, would be necessary, the Pi itself wouldn't be airgapped, right?

Edit: depending on how the QR code was provided to the Pi. I guess the Pi wouldn't necessarily have a camera to get the QR code, and then might not be airgapped from the source of the QR code. Seems to me the USB, however, would be a mechanism to airgap between the source of the data and the Pi, with only the USB drive connecting the source of the data and the Pi.