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..