Depending on what your goals are just adding a Bluetooth keyboard to an Android E Reader gets you 90% of the way there.

https://shop.boox.com/products/go103

I dabbled in hardware and I quickly found you need millions to do anything.

However, this definitely is a market waiting for a product. I’d lean towards looking if you can add a custom screen to the framework laptop.

That’ll be much cheaper to build and easier. I reckon you’d only need a custom Linux driver for the screen.