I have an older HP Photosmart C4600 series printer where HP no longer supports the driver and there doesn't appear to be Airprint drivers for this either. Was working until recently. Any recs. for resolving?

I am sorry you are having printer problems. If you will bear with me, I will offer some things to consider. Whenever we install an operating system upgrade or some OS updates, printers and scanners will often stop working. Then a new OS compliant printer driver must be installed. Experience has shown that many printer manufacturers are very slow to provide updated drivers. Drivers for some older printers are never provided. (Apparently, they prefer to sell new printers.) What we can do is to thoroughly check the printer web site for an updated driver that works. If one is not available, then we should ask when one will be released. If that doesn't work, then you can check the web site below where volunteers write drivers for older printers which are no longer supported, but which work with newer operating systems. It is worth checking out. Good luck.

Gutenprint Supported Printers

Incidentally, if Air Print were available to be used, it does not use any drivers and any installed drivers should be removed.

Try the following:

reset the Print System https://support.apple.com/en-gb/guide/mac-help/mh14001/mac

then Install HP Smart for Mac Desktop from the Mac App Store https://apps.apple.com/gb/app/hp-smart-for-desktop/id1474276998?mt=12