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Yet another way how to backup persist (or any other) partition even without PC, with rooted phone and Magisk: Install Magisk module "backup" and reboot. After that using some terminal app in phone (I use Termux), first gain root access: su and then enter backup persist it will create file persist.img in folder /backup of your phone's internal storage. The path can be changed of course. I suppose same can be achieved with dd command, but the above is easier. Instead of terminal app in the phone you can of course use adb shell from a pc.

FWIW, the USB bug with modern Ryzen systems has been fixed in SDM662 and Fastboot/EDL works fine on my system. No need for the USB 2.0 hub if you have the 1X I guess.