A ReMarkable 2 with the Folio keyboard is almost a whole ass computer. An eMacs-like development environment where buffers also had layers that could intermingle strokes with text and it would be perfect.
I’d hack my own but I’m a little paranoid of bricking it with only one hardware button.
I put code-server[1] on a Linux box of mine, which gives me a whole proper IDE in the browser. I use it a lot on my Boox tablet with a bluetooth keyboard and it works great.