[geekmaster]

I will try the original method. A downgrade requires really old firmware (which I do not have).

I cannot find (at the moment) my big box-o-devkits (with bus pirates and serial adapters and such) -- a side effect of spring cleaning, I am afraid (where stuff not used recently gets "put away"). I hope the original method works so I do not need to keep hunting for missing hardware tools.

Though I suppose I could do a little proxy app to make a kindle into a usb serial adapter SSH into the kindle, then run another terminal app that talks to its serial port which is wired to the target kindle serial port. A lot of us have more than one kindle, or would likely wouldn't be here in this forum, eh?

But I prefer the USB-only methods when available.