JPR

I had exactly the same problem (no Colour Matching option) when I first used AP with Big Sur and my Epson P800 printer. Like you I checked Epson for new drivers, with no luck. However simply deleting the printer from the System Prefs>Printers list, and then adding it again, cured the problem. Worth a try with your P600?

I am also having strange colours, with half of them missing, when printing with a Canson icc paper profile selected. I'm using 1.8.6 on an iMac with Big Sur and printing to an Epson SC-P800. The profile works fine with other apps on Big Sur, but not with AP - I get a pale weird looking print that is a washed-out version of what it should be. If I don't use the Canson profile, but let the printer deal with the colours, the AP prints a reasonable version - but obviously the colours are not as correct as they should be. I really need to be able to use the custom paper profiles to get accurate colours..