I had to laugh at this. At least in my use case, it’s printing out forms and documents that various levels of government needs and I am absolutely not talented enough to reproduce them by hand (also, my handwriting is not fantastic).

If we want to get pedantic, it is possible to get a pen plotter. There are fountain pen compatible pen plotters, and the whole fountain pen world has a healthy and mature third-party ink market.

Now, that’s not simply a drop-in replacement for a regular printer, starting with the fact that you need to use monoline fonts so that the plotter traces out what a hand would rather than filling it in, and that a plotter just can’t produce all the same stuff. The speed is going to be abysmal compared to a conventional printer for virtually any image. And I don’t know if there’s anyone who has built one with a paper feed system (there are large-format pen plotters that can work with a continuous-feed roll of paper, but I don’t know if those can handle fountain pens. I don’t know of a fountain pen plotter that can just take a ream of A4 or US Letter pages and then handle those correctly).

But you can, strictly-speaking, have a computer create output that uses ink from the fountain pen world.