Manjaro Linux, AppImage of
RawTherapee_Beep6581_whitebalanceopt_release.AppImage
I assume that the CR3 from the EOS R7 is not fully compatible. I am able to fix images such as this one with the eyedropper, clicked on the background.
Are you using the 5.9 production release? I don’t think CR3 files are fully supported yet. I recently purchased a Canon R7 too and found other CR3 issues, namely there was no meta data available. So, I tried the Adobe DNG Converter which worked fine but there was the extra step converting the files. I have since installed a DEV build of RawTherapee from a few weeks ago and everything is working great now! You can download installable builds here:
The whitebalanceopt branch is 250 commits or so behind dev or release-5.10, I think @desmis was working on it back in July. I recommend using either of the other branches for CR3 support.