I searched for each of the supported eInk devices and they were all tiny. Anyone know if there is a larger reader (maybe Paperwhite size-ish) that might run this?
I've never heard of any of them; I guess it's geared toward build-it-yourself or kit-type devices? I can't imagine a serious aftermarket FW not supporting a single Kindle or Kobo device.
ESP32-S3 is really too underpowered for larger e-ink devices.
The "Hardware" link indicates that the BoM specifies a "24-pin SPI e-paper for GoodDisplay panels (3.97″, 4.26″, 7.5″ and up)." A search turns up this: https://www.good-display.com/product/516.html