Oohh, a customer…
In another thread, I’ve been working on a graphic that describes generically how color is managed during raw processing. Here’s a link to the post containing the latest (well @Claes and I worked on a subsequent version, but the differences are just editorial):
Color Management in Raw Processing - #92 by ggbutcher
I’ve also started accompanying prose for a blog post, but it’s not ready for prime time. Some of the “color science” that can differ from software to software is in the camera profile; most FOSS software seems to start with the primaries from dcraw, a command line raw processor that in turn gets a fair bit of it from the Adobe DNG Converter. RawTherapee has a file, camconst.json, that is worth a read in its own right; not only does it contain user comtributions for better color information, there’s a lot of commentary at the top as to what it all means.
Regarding thumbnails, a lot of software just pulls the embedded JPEG out of the raw file, already developed by the camera. Don’t trust them for comparison…