Another upgrade annoyance.
I have hp 1020 laserjet usb connected. It worked great everywhere, until last night on Mint 21.
I checked settings (localhost not cups.sock, shared, and service started), removed and reinstalled repeatedly.
Then i realized i needed hplip. But Mint said i had hplip. So i downloaded the latest version from the HP website. It could not install on Mint 21 due to unmet dependencies that could not install either.
If you are trying to install the latest hplip inside the package system , that is not a good way to do it. The version of packages that come with Mint21 are tested to work together. If you add in a newer version of a package it may have incompatabilities, as you gave seen. you might get away with it sometimes, but it is not a good practice
The right way, if you want to add something that is outside Mint21 , is to install it in either /usr/local or on your home directory.
What makes you sure the new hplip is needed? Mint21 will have a fairly recent version. I think your problem is likely to be somewhere else, probsbly in the CUPS setup.
I can now set this as SOLVED.
I went into Synaptic, searched for hplip and lo and behold, there were several important packages that had not yet been installed.
I installed them, did a little fiddling, the HP software found the prnter and set it as default.
Well, Mr Neville, I wish I had read your answer earlier.
The reason hplip is necessary, though, is that test pages are reported as printed, but the printer remains silent.
I just ran a test page and it now works.