You have a stash of 3rd party cartridges and don't care about security patches. No, if: You use HP Instant Ink or genuine HP cartridges.
A key "new" feature for the HP Officejet Pro 8620 firmware downgrade is the Automatic Update Lockout hp officejet pro 8620 firmware downgrade new
"Now comes the hard part," he muttered.
On your printer’s touchscreen:
Do not host the firmware file directly on your site (DMCA risk). Instead, link to a "How to extract from HP's own archive" or a checksum hash (SHA-256) so users can find it via archive.org. You have a stash of 3rd party cartridges