Custom Firmware for Printers

Yes, of-course there is.

Your question is a bit vague, particularly you don't mention which printer. You can get generic ink/cartriges/refills for most printers, and they work fine. Some of the cheaper printers (Like the Samsung Color Laser I have) have DRM to limit the use of consumables. But you can purchase firmware unlockers on eBay which works just fine. In my case I get the toner in bottles and pour it into the cartridge via a hole which needs to be sealed off with a stopper or duct tape.

You can also invest in aftermarket ink/toner from eBay or elsewhere online. You do need to be a bit careful though, because the ink needs to be suitable for your printer. Not all printers use identical inks.

Some brands like Brother Printers make life very easy. You just remove a cap and pour the toner, no hacks required.

You also get CISS (Continuous Ink Supply System) for Inkjet Printers which allow you to get bottles of aftermarket ink and feed this into an inkjet printer.

Again, I think most brands are supported but Lexmark and HP are the main ones. I believe this is good if you are doing volume printing, but is not always a simple, pleasant experience.