I just went to the dev. page on the website (development | darktable) and noticed the two links at the bottom under “Supplying a color matrix…” are timing out. I wasn’t sure if this was something I should put on GitHub, so I thought I’d mention it here first. If there’s a preferred place to report it, lmk!
Unfortunately Pascal’s website no longer seems to be up. We can change the link to point at archive.org I’m sure. I don’t even know if this information is still needed.
custom color matrix was used in early darktable versions and are pretty outdated now.
If a camera support is added then a proper color matrix is available which is usually better than an arbitrary user generated matrix.
If this matrix doesn’t fit to your camera then your camera might be deviating and not representative.
But you can use it for your camera via an input profile and a preset that’s auto applied for your camera