Most USB devices shouldn't interfere with the update - USB keyboard and mouse are no-brainers, hubs too, should pose no problems. Obviously any device using the Steinberg Yamaha driver should be disconnected as already stated, I would also disconnect any devices concerned with MIDI.
Consider too, if you follow the update instructions to the letter, disconnecting everything on USB except mouse and Keyboard, your chances of success are maximized, and should the update prove unsuccessful or exhibit any errors, there are no open questions that perhaps this or that device might have caused said corruption.
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