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.
I have the same Kindle as the OP and very nearly bought the Xteink4. However, they wanted $28 to ship to Alaska, which put me off buying it; my Kindle Touch still works fine after many years and one battery replacement, though it's slow compared to newer E Ink devices.
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