Unplug the LAN cable, uninstall the LAN drivers, connect the printer via USB, and install USB drivers. Some users are reporting trouble installing the firmware, so be sure not to use a Wi-Fi connection. User fmillion had summarized his steps within this post. There is another article here, providing hints for installing firmware updates on HP printers (and with an old firmware, it's a downgrade). I can't test it due to lack of a printer, so note that downgrading is at your own risk. Blog reader Matias de Goycoechea posted instructions on how to proceed in this comment (thanks for that). Users have to do downgrade manually by installing a saved old firmware version onto the printer. HP printers do not have a simple button to switch back to the old firmware after an automatic update.

Thanks to these articles, I get to know relatively quickly when such an HP action has happened again.

2020) – but there are other posts on similar actions at the end of the article. I reported on this practice the last time within my blog post HP firmware update for ink/laser printers blocks third-party cartridges (Nov. Hewlett Packard (HP) has a nasty surprise from time to time for its customers: They are blocking the use of third-party cartridges via firmware updates. HP blocks third-party cartridges via firmware

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