I’m currently in the process of building a case for my Raspberry Pi 3 with a 7” LCD (switchable, so one can use the HDMI instead) and a mechanical keyboard, that boots into my own custom “distro” of Linux that is basically a pure TTY, some fonts, a BusyBox shell and Wordgrinder.
While I’m missing the difficult bits (the case, the battery, the switches and so on — I want to be able to use it as a word processsor, a “home computer” plugged into the TV, and a pure keyboard depending on what switches are flipped!) it works wonderfully for distraction free writing.
Ctrl-Shift-F1, ‘$ wordgrinder’ and away we go! Best part is, I can swap the SD card out to get the data off it without needing network abilities. Think of it like a DIY Freewrite (née Hemingwrite)