99% of this is the printhead and the ink formulation. Assuming you use generic off the shelf solutions for those two components you’re set. All the printer companies do their lock in at the firmware and software layer.

Yeah, I found that original comment to be a bit nonsensical. It would be like arguing you can't build your own PC because the lithography tech needed to make modern ICs is really complicated. I wasn't planning a laying out my own chip, and these guys aren't planning on building their own printhead from scratch.