Thanks FlyingAppleFortress, your detailed description made me dig a bit deeper and I found a solution for my problem thanks to you, indirectly.
I executed your steps a few times without any positive result, but I also noticed that adding the printer through the macOS Printers & Scanners panel, generated a file called “HP_6970_Air.ppd” (“HP_6970_Air” being the name I gave to my printer) in /private/etc/cups/ppd. That did NOT occur when using the HP Easy Start software. Examining this file with a text editor, I discovered these 3 lines at the end of the file:
*APScannerUUID: "DF5BC5D6-3939-F1BF-D7B7-0C11C773A409"
*APICADriver: True
*APScannerModulePath: "/Library/Image Capture/Devices/HP Scanner 3.app"
But there was NO HP Scanner 3.app in /Library/Image Capture/Devices/ !!!!
When I looked in my old MacBook Pro running Sierra I found that the same PPD has a different path and file for what I assume is the scanner driver:
“System/Library/Image Capture/Devices/AirScanScanner.app"
So I checked on my Macbook Air M2 and lo and behold, the AirScanScanner.app file was also present in the same location.
I then edited the “/private/etc/cups/ppd/HP_6970_Air.ppd” file to included that same line at the end and Presto! my scanner worked again.
Now, a word of warning, my recall of the steps might be a little troubled and I might have executed some other steps in between or repeated one or two a few times, like rebooting and emptying the bin, but the end result is that
- there exists a “/private/etc/cups/ppd/HP_6970_Air.ppd” file and
- the last line in that file says *APScannerModulePath: "/System/Library/Image Capture/Devices/AirScanScanner.app" and
- there exists a “System/Library/Image Capture/Devices/AirScanScanner.app” file.
So if you can somehow make these conditions true, you should be good, like I am now, after 3 days of swearing and hair pulling. If you want to try this, subsitute “HP_6970_Air” for your own printer name of course.
Good luck