Workflow: coloured illustration to b&w

I am working on color illustrations like the one attached.
I should turn them into monochrome graphics, keeping as much as possible “only some” small shading/shadows and mainly the black pen strokes.
Currently the workflow i’m using involves :desaturation, more contrast, parametric tone curve for shadows and highlights, tone mapping with strenght 1.5, edgeS. 0.2, and scale in according to the specific graphics.
I am not fully satisfied, and I am not able to use all the advanced LAB color settings.
I could do it if I had some info on the direction to go. Can you give me some additional advice to respect the overall stroke and eliminate/flatten shadows and gradients?
Another strategy i’m using is to apply the settings I just mentioned and then a second step of adjustment using black value, contrast and tone mapping again.
So of course I notice sometimes that micro details are eroded and lost.

coloured original
b&w edited

Thank you very much

Hi Marcom, I am probably not 100% sure what you are trying to achieve, but I downloaded your files and looked at the adjustments in GIMP and Rawtherapee.

GIMP has a monomixer that might be useful for the greyscale conversion. GIMP also has the ability to do layers and masks so you can do different conversions to different areas of the image.

Rawtherapee has the Black and White module which might be useful.

The idea with the monomixer (GIMP) or the Black and White module (RT) is that the image is not just desaturated, but rather the various colors can be adjusted to lighter or darker shades of grey. Back in the days of film, colored filters were placed on the lens as contrast filters when shooting B/W to create the sort of effect we now get with these tool options in digital editing.

Good luck