@soenke.heuer : I have taken a quick look this morning and the Affinity output is not entirely neutral in the recovered highlights, i.e. yellowish. I’m wondering at which step they are performing the recovery and if there are any colour tweaks post recovery because their gray patches are properly neutral while the recovered ones are not.
Any clipped highlights is technically garbage and cannot/should not be used. Usually cameras being most sensitive to green as per Luther-Ives condition/Luther criterion, the green channel will be the first to saturate/peak hence the magenta cast you get when highlights are not recovered.
My process when recovering highlights is roughly to assess which channel peak first, then anything above is desaturated. There are fancy papers/algorithms using colour restoration in image gradient domain, e.g.  but because clipped data is garbage anyway, I never bothered implementing anything like that: it does not make any sense from an accuracy standpoint and can potentially have side effects when generating HDRs.
I have processed your image with my tools, white balancing on the Neutral 5 (.70 D) patch using CCT=6600, Duv=0.0017:
The lack of punch from my output is because there are no fancy curves, e.g. Adobe Camera Raw Tone Curve applied in my process.
I’ll get in touch with @mzhu and @Alexander_Forsythe to see how things can be improved on rawtoaces end.
- Lau, C., Rouf, M., & Heidrich, W. (n.d.). Gradient Domain Color Restoration of Clipped Highlights. Retrieved from https://www.cs.ubc.ca/~heidrich/Papers/PROCAMS.12.pdf