How to get Custom Printing ICC profiles working in MacOS
As a photographer, I have struggled a lot trying to get custom icc profiles to work when printing from MacOS. I find that certain applications, like Canon's Professional Print & Layout, internally know how to communicate with the base MacOS printing driver and indeed apply the profiles correctly and prints come out looking great. I've had a lot of trouble with Adobe applications. Long story short (and caveat, I think other users might have different experiences here), I found that in order to use custom icc profiles correctly, one needs a software that allows selecting a custom icc profile in-App, like in Photoshop's print dialog; and on top of that, one has to go to the MacOS's Print dialog and make sure that under Color Matching, "ColorSync" is selected and "Generic RGB profile" is selected too. In the same MacOS printing dialog, under "Printer options", some printers might require "Color Correction" turned off also.
For my workflow, this means that I can't print with custom profiles from applications like MacOS's Preview or ColorSync Utility (Preview doesn't even allow selection of a profile and with ColorSync Utility, I need to set ColorSync to "Generic RGB Profile" and I'd need one more layer on top of that to select the correct custom icc profile). That's ok, since most of my color-sensitive material will anyways come from a color managed app like Adobe's or similar.
Hope this helps people ease frustration and save precious ink and paper.
MacBook Pro (M1, 2020)