Rather than all that to turn an e-reader into a tablet, consider a general tablet that's an excellent outdoor/travel e-reader already:

https://daylightcomputer.com/

2004: https://news.ycombinator.com/item?id=40456834

It's not e-paper, it's a different approach called "Live Paper" that's far more practical for everything beyond reading, yet still fantastic in direct sun:

https://www.slashgear.com/1655111/daylight-computer-live-pap...

Pair it with a slotted Macally keyboard for travel with a stand slot and 3+ mos charge:

https://us.macally.com/products/ipad-keyboard-bluetooth-mac-...

This fits in the Daylight computer pouch.

For reading, use Kindle (or any Android reader) in landscape 2 page mode for an experience that's like reading a paperback, or portrait for textbooks/PDFs. Work beautifully in the brightest direct sun, or read with calming firelight colored backlight in the dark.

Runs M365 suite perfectly, so ideal as an all in one.