I am pleased to see that the forum is popular, and indeed you get results, but still no communication from iRex.
Finally I am resolved, in agreement with reference professor, to open the device and to extract even a serial port on the Hub (see the photos and the electric scheme about the contacts that are unused:
https://www.mobileread.com/forums/showthread.php?t=7416).
To open the device is needed a torx screwdriver (or imbus); I buy a "Beta 1255tx 5" screwdriver. Moreover, for everyday use is of course required a second travel hub: to access the logic board is necessary to break the little box of cast plastic.
The operation should not be too invasive or dangerous, but obviously void your warranty. I think I will post a guide for the whole operation.