There are many ways to do this, either fiddly or a little expensive. You can

- use a Dasung screen or Boox Max with your desktop (expensive, plug and play)

- use a hacked-up Linux e-reader (super cheap, fiddly)

- build something with WaveShare kits and an Arduino/Raspberry Pi (moderately expensive and fiddly, but allows for interesting creations)

- use some app (Termux) on an Android E-Reader (Boox, moderately expensive, quite versatile).

The tech is a bit inaccessible, but not as much as it may seem. Just check out: https://hackaday.com/tag/e-ink/

I have a number of Dasung products and the results are spectacular. I can code for hours on end with no eye strain and my sleeping schedule is normal for the first time in 15 years. The lack of flashiness on the screen also lets me think more about what I'm doing.

i think you can do it on an Onyx ereader with a vim terminal android app. For sure, I've run Vim on an Onyx with a BT keyboard. Worked ok. Not sure about a full blown vim terminal. I know the apps exist on playstore.