[grishka]

That's why I'm talking about a replacement motherboard for an existing consumer-grade printer (though not necessarily an inkjet one, I don't get it why people keep buying inkjet printers when they don't intend to print photos). Custom PCBs are very easy and cheap to get manufactured. All the maliciousness of these printers is in the firmware, and replacing the motherboard with an open-source one feels like the easiest way to get rid of that. The other possibility would be to write a custom firmware for the stock motherboard, but I'd imagine that printers these days would have some form of secure boot.