Here's another version similar to my last, but with use of Darktable's equalizer module on the skin.
Mairi_Troisieme.ORF.xmp (61.0 KB)
I wanted to see if I could do something similar in Darktable to the wavelet decompose method you show in GIMP, @patdavid, and with some simple masking I think it's working out. It's not done to anywhere near the same level of finesse as yours, but I'm pretty stoked that I've managed to get an effect that's starting to move towards the look without having to leave Darktable. Further experimentation required!
The relevant modules are pictured below in case it's useful to anyone. 'equalizer 2' is applied to most of the face, barring the eyes and eyebrows, nose outline and mouth. 'equalizer 3' is a stronger instance applied to just a couple of areas. Both of them actually increase luma contrast/detail a little for the finest couple of wavelet-based levels of detail.
I imagine this tool will also be extremely useful in other types of photography, such as landscape. Thanks so much for sharing information on this method! I'm looking forward to playing with it more on some of my photos.