Michał, thanks! /usr/lib/cups/backend/usb is indeed not part of a package either, it's a hardlink created at postinst time.
So that's the missing piece of the puzzle.
Michał, thanks! /usr/lib/ cups/backend/ usb is indeed not part of a package either, it's a hardlink created at postinst time.
So that's the missing piece of the puzzle.