The printer screen will display a "Flashing" or "Updating" message.

Open the downloaded older firmware executable file on your computer.

Firmware updates often introduce new bugs that HP takes months to fix (or never fixes).

Old SMB v1 and v2 protocols (which HP killed in later updates) return. You can scan directly to a Windows 10 or NAS shared folder.

To be clear, HP's Dynamic Security list specifically includes the OfficeJet Pro 8620. The consequences for users include: