just to clarify – color calibration is for correcting colours under a particular illuminant against the reference values for the colour charts – ie. standardising the colours. It is an altermative to producing an ICC matrix profile for your camera.
darktable-chart can also be used for matching colours between JPEGs – in that case, the JPEG you are matching against is already a display-referred image, and so using display-referred modules probably makes sense in that case.
Yes, my primary target is less to calibrate for the correct color according to a color chart, but rather to make the Canon picture profiles available that provide different color matrices from RAW to JPG. While using Lightroom I never used the Adobe standard profile (which to my understanding is the darktable standard input color matrix) but rather the best fitting Canon color profile. So ideally these should be available as input color matrix. But applying the Color LUT created by darktable-chart at the end of the pipe is a possibility. Thanks for the input.