Well, jailbreak applied. Can't get SSH working on it yet (because it is late and I am tired).
But it is old enough that the DRM can easily be stripped off any legitimately purchased books.
So, for the few authors who insist on *only* releasing on Kindle, I can now read on my other devices.
Not bad for a night's fiddling.
Oh! And this #Kindle is so old it doesn't support 2FA.
The officially supported way to log in is:
Type email address.
Type password.
Hit submit.
Wait for an error message.
Type password123456
Yup, literally append your TOTP code to the end of the password.
If it's stupid but it works… Well, it is *still* stupid. But let's not quibble.
Luckily, since Debian Stable is reasonable, the repository still has 8.5.