I've read a lot of difficulty here on this topic. With all the help I've gotten here, I thought it would be in order that I share something I eventually solved. I'll skip the gory details of the saga, other than I've read that techies are often frustrated by the lack of HP support.
My HP Photosmart printer/scanner was working upon Z16 installation, but at some point it became defunct and I went through all the hoops I read here about.
WHAT FINALLY SOLVED IT FOR ME: 1) On the physical printer intself's panel, I hit "Restore to Factory Default" (I don't really know that to be relevant). 2) unplug printer/scanner & make sure it's removed from settings GUI. 3) From How to Enable & Disable AppArmor on Ubuntu 20.04 - LinuxCapable sudo systemctl stop apparmor . 4) Replug printer/scanner & ADD printer in GUI. 5) Then I was able to use the defunct scanner function again that I thought became "bricked". 6) sudo systemctl start apparmor .
Evidently the native AppArmor was causing an obstruction.
For whatever that was worth, I hope it helps.