Colour Management was working yesterday (such as it is on Painter) but today it does nothing. Assigning profiles, Converting, Colour Proofing, none of these make the slightest difference to the image. I've SHIFT-started Painter and cleared all workspaces but this makes no difference.
Has anybody encountered similar asshattery and if so, did you solve it?
Meanwhile I've downloaded Krita, which is very accomplished at Colour Management and is the only package aside from the extremely expensive Photoshop to properly cater for CMYK.
Just discovered Affinity Photo. Not for painting, Corel Painter still excels in that by a huge margin, but for post-processing and CMYK. Amazing.