After having NO success 10 days ago printing on a very old yet perfectly fine HP printer (HP Photosmart C4480) with the Big Sur OS on a late-2015 iMac, I have SUCCESSFULLY printed on it today! So there is hope; hang in there.
Here is what I did. I am not tech-savvy enough to know what worked. But I offer this in hopes that you may find it helpful.
- I installed the latest Mac OS update (11.1), which included restarting my iMac.
- I ran the HP Uninstaller. Then I searched with Finder for any remaining programs named HP. I found two -- HP Smart and HP Uninstaller. I dragged both to Trash and emptied the Trash.
- I restarted my iMac.
- I connected my C4480 printer to the iMac with a USB cable (so quaint, but the printer is so old it does not have wifi).
- I commanded a Word doc to Print. I received the ominous "will damage your computer" box. I clicked on Show in Finder. Then I went back to the Word doc and clicked Print again. This time I was given a box to select the printer that did not show the C4480. I clicked Add Printer. Now the C4480 choice appeared. I chose it and -- the doc printed!
- Unconvinced, I printed the doc again. This time, no warning, no events, nada. Just a print. (Happy dance!) Back to normal operations. (I haven't tested the scanner.)
My guess is that the newest Big Sur update quietly fixed this problem. (The notes on the update say nothing about printer errors, however.) But who knows?
Thanks to Jan Hedlund and others here for very kind, helpful and plainly worded suggestions. One other thing I learned from this event, and your posts, is that my late-2015 iMac may not be supported much longer in OS updates. So, I am turning off auto updates. I will check for compatibility before any updates.