I’m a bit baffled too, but LittleCMS is something I’ve looked at before. Two years ago I started this thread
which showed LittleCMS did in fact deliver a difference between perceptual and colorimetric output intents. At the time I reckoned it was therefore doing a decent perceptual rendering, which was what I wanted, providing I used the sRGB_v4_ICC_preference profile, and not the default sRGB websafe. I’ve been using the former ever since. What baffled me was that its perceptual intent looked the same as sRGBwebsafe with any intent, so I wondered if that had somehow been made perceptual.
Anyway I just re-tested with 4.0 and there’s still that difference between perceptual and abs.colorimetric using LittleCMS and the preference profile.
Are “gamut mapping” (as per Aurelien Filmic 6) and “traditional” perceptual intent two ways to achieve the same goal i.e. reducing gamut for your output step?
It was only a few months ago when I read that apparently LittleCMS does not work properly.
Edit: before “What baffled me was that it looked the same as sRGBwebsafe with any intent”
after “What baffled me was that its perceptual intent looked the same as sRGBwebsafe with any intent”