In Linux it's pretty easy to create such things with cups. A while ago I did a cups backend for my Fujitsu Quaderno A4 [1]. It is super useful to be able to just open any document, in any program that supports printing, and then just "print" it to my device.
Unfortunately printing support seems to go out of fashion, at least in macOS land.
Lately I needed a quick printout of a markdown document. I could have used TextEdit for the raw text, but I wanted the styling too. Learned that neither VSCode, Xcode nor Obsidian can print. (There is a community plugin for Obsidian.)
I see that it applies styles to markdown documents, but keeps all formatting characters visible (e.g. # for titles). I guess I wasn't happy with that and looked for another solution.
> printing has never really been a thing from text editors I think.
It's always been a thing: We programmed on paper before we had screen editors, and so early screen editors have always had a way to murder trees on demand:
In vi it's :ha
In emacs it's M-x print-buffer
> It has been a while since I printed a plain text file, but I guess there's still a similar command available with some research.
`lp myfile.txt`
I still prefer using hardcopy for reading/debugging.
I think back in the days before office workers that happened to do their work on a computer had access to the ancient relatives of "Microsoft Word"/"Libreoffice Writer", it was pretty normal for printers to take care of plain text files, with about as much fidelity as manual operation of a classic purely mechanical Typewriter.
Since then printers progressively forgot how to cope with such "documents", though IIRC good-old HP "PCL" should only require about a bare minimum of framing/job control to get a modern printer to handle ASCII plain text.
I used to print a lot of code from Geany, that has some nice support for printing line numbers and code highlights that I have a hard time replicating in other tools.
[1] https://github.com/cristobaltapia/dpt-rp1-cups