Depending on what components were upgraded a downgrade is not a 100 percent guarantee fix. You need to find the old update executable file, open it with 7ZIP and extract the .ful2 file from it. Copy that file to a USB stick and then insert the stick into the usb slot on the printer. Most printers will recognize the presence of the file and prompt to upgrade/downgrade or you may need to reboot the printer to get it to happen.
No defense of HP, but EVERY vendor does their best to ensure customer's buy OEM cartridges.