@londons_explore @ Hacker News:
I found a surprisingly simple workaround...

Put a resistor, about 1kohm, in the power line to the security chip on the cartridge.

Now, whenever the printer tries to read data from the chip, it works. Whenever it tries to record data to the chip (for example, marking the cartridge as empty), that uses more power, and the memory chip doesn't respond.

Amazingly, the whole setup just works and prints forever, saying the cartridges are always full...