Thank you, qadzek, for telling me about LunarEclipse's work - that has solved my problem. Amazon login was not needed.
I had been experimenting with blocking Amazon hosts, and LunarEclipse had a lot of new addresses, and now my jailbreak is no longer disabled after adding them to my hosts file:
https://github.com/Darthagnon/kindle-kual-blockamazon
https://codeberg.org/LunarEclipse/kindle-block-amazon
Thread solved!