Kindles are fun devices to hack and play with. I can grab an old kindle for €15-20 on eBay.
I did the same last year and had lots of fun in the process.
For the less reverse-engineering prone among us, there are also similarly sized e-ink displays that plug into Raspberry Pi DSI ports for maybe $5 more on Aliexpress. They might actually be salvaged kindle screens.
I love it! Always fun to see the route somebody else took to get to the same end product.
Your post is making me want to try more Cloudflare Developer Platform stuff like Cloudflare Workers.
Can you start jailbreaking straight away, or does it require an internet connection and Amazon account first during setup?
There is also the Xteink4[0] that can be purchased on Aliexpress. It's just an ESP32 with an e-ink screen.
It costs more and is smaller but when you are done playing around with it you can flash it with Crosspoint[1], carry it in your pocket and read books on an e-ink display wherever you are.
[0] - https://www.youtube.com/watch?v=yMoq17-1pJA [1] - https://github.com/crosspoint-reader/crosspoint-reader