Sytem Diags - D - In some versions, that is: "exit to command line"
Misc Diags - M - Might exercise / test eMMC and just the label hasn't been changed (Kindles once used MoviNand devices)
Utilities - Z - enable USBnet - that might let you ssh into the Diags command line
- M - Do you have an nfs server set-up (it is usually included by default in Linux distros)?
If so, we could try mounting the "Main" file system over nfs (just as if we where developers

)
That one we get a root system image by opening up an Amazon update package with KindleTool.
Also worth exploring: W and F
Backing up 'Diags' - -
We don't want to do it while mounted and running - and 'Main' isn't working (unless we can net-mount a good copy).
Sticky "Where do I start?" -
It will be among the "legacy" de-bricking things.
But the 'Diags' system is evidently burned into the eMMC while still on the tape, before being mounted on the board.
Then it is never changed, so anybody with a working PW-2 can donate a copy if we need it. (NiLuJe has a PW-2, when he gets time to return here)