YOU DO NOT HAVE THE PERMISSIONS! Ugh. Upgrading to Big Sur 11.5.1 murdered my old flatbed scanner, which I use all the time. Evidently, it's a problem for many many many people. The following sequence worked, but I can't guarantee that it will work for you as well, since I deleted, added, re-deleted, upgraded and downgraded all kinds of files until it finally showed up without an error: Delete the scanner from Preferences Delete Canon utilities Remove any Canon-related files from /Library/Printers/Canon Remove any Canon-related files from /Library/Image Capture/Devices Reboot Install the misd-mac-ijscanner2-4_1_4-ea21_3 driver Don't install the LiDE 210 Scanner Driver Ver.18.2.0 (Mac) file, that seems to be both useless and part of the overall problem. Just use Image Capture and you should be fine.
Here are the solutions I find on my own once customer support tells me they've exhausted all options.