I ran all the tests in X11.
With the patches and `logleve=verbose`, I get this message:
[swscaler @ 0x7f1c4c061040] deprecated pixel format used, make sure you did set range correctly

With AppImage, i.e., without patches, I see the same behavior. Without `loglevel=verbose`, no messages appear in the terminal.
I'm not sure if your patches work on my system. Or maybe the problem is my monitor's color profile (wide-gamut with BT.1886 gamma). Since I can no longer disable or change it (that's the problem that made me switch to Wayland).

When I use Redtruck_GBR.jpg in both the AppImage and the CinGG compiled with the patches, I see the blue truck and the green sky. So that proves your patches don't work on my system (KDE). I used the three patches: 0001, 0002, and 0003. Maybe I should also use the lcms2_transform.diff patch?
Do I need to use any options in ./configure? I had already added the flags2=icc_profiles tag to decode.opts

CIN_CM_PROFILE="/usr/share/color/icc/colord/WideGamutRGB.icc" /home/paz/cinelerra/cinelerra-5.1/bin/cin /home/paz/wide-gamuts-tests/*.jpg still isn't working for me, even after removing all non-JPG files from the folder: same error. Maybe your patches only work when launched from the terminal, and not—as I normally do—from a desktop shortcut to which I've added CIN_CM_PROFILE="/usr/share/color/icc/colord/WideGamutRGB.icc"?