The author mentioned them already, but didn't recommend for violating the GPL, but I have an Onyx Boox Poke 3 and Boox Leaf that run Android that I've rooted. They're not very cheap (the Poke runs about $180). They're pretty fun devices to tinker with. https://chuck.is/rooting-onyx/
Edit: I also experimented with the Poke 3 by creating a sort of "writerdeck" setup with a bluetooth keyboard and termux, then attaching everything together with velcro and magnets: https://chuck.is/writerdeck/
Edit: I also experimented with the Poke 3 by creating a sort of "writerdeck" setup with a bluetooth keyboard and termux, then attaching everything together with velcro and magnets: https://chuck.is/writerdeck/