Oh, the broken implementations don't stop at backwards compatibility -- Lightroom CC, their new Cloud product, last I checked, prefers to send sRGB to Photoshop (!) unlike the traditional Lightroom which fully supports preserving embedded colour profiles when exporting. It's been a couple weeks since I looked into this but the instructions in this post https://lightroomkillertips.com/keeping-your-color-consisten... apply to Classic Lightroom if I recall correctly, and the modern "cloud" Lightroom CC only exports wide gamut correctly when set to export as uncompressed TIFF 16-bit. Everything else tries to export as sRGB automatically, which sucks for print or DCI-P3 workflows.

Also, I'm trying to find details on Apple's P3 profiles in how they differ from standard projection profiles for the movie industry to maintain compatibility with sRGB gamma, but there's not as much online as I expected about it.

In my search for info, I came across https://ninedegreesbelow.com/photography/lcms-make-icc-profi... which seems like a useful resource for Linux/FLOSS folks.

Ah. Found it, a source for the differences between "Display P3" and movie-theatre P3. Here's a link to the relevant section of the video, on colour spaces: https://developer.apple.com/videos/play/wwdc2016-501/?time=2...

And here's a good discussion on why D60 was chosen for film projection while D65 is used by modern computers for sRGB/Rec 709 compatibility: https://www.liftgammagain.com/forum/index.php?threads/dci-p3... and here's a bit on the technical details of ICC profiles and CIE XYZ numeric representations of colours: https://ninedegreesbelow.com/photography/xyz-rgb.html