I can't use my HP Laserjet 1012 after MAC upgraded operating system

Hi,

You may want to try a fresh Dec 11, 2020 HP Printer Drivers v5.1 for macOS download from Apple at https://support.apple.com/kb/DL1888?viewlocale=en_US&locale=en_US . Look for an HP LaserJet 1012 driver (2.0.4).

It may be a good idea to reset the printing system to begin with.

Reset the Mac printing system to solve a problem - Apple Support

Add a printer on Mac - Apple Support

I'm on Big Sur and my LJ 1012 (must be closing in on 20 years old) works fine. What problem are you having and how is the printer connected to the computer?