If you want a quick answer, copy the uSD card from the working system (you can do it with an SD card reader) and then swap the two cards.
Due to the small size, booting from an external USB increases the portability. As far as I know, this was also the goal of zbitx, to be small and portable.
By the way, if you want to experiment with this external USB boot, you can read the solution on the JJ wiki how it was implemented at sbitx.
The microUSB is probably usb 2, so I think you can't achieve a speed increase with this.
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Gyula HA3HZ
HA3HZ