Hi ! thank you.
I managed to make it work at least …fairly. Now the shrink wrap renders as I was expecting (with the shape of the shrink wrap target. What I did: I pressed the invert vertex group button:
Might be that the vertex assigned are wrong? i have my vertex group created, but empty in a way no vertex are assigned. It worked well with other mesh. I copied the technique from another user in the forum.
I am not sure why by pressing the invert button worked (since nothing is actually assigned).
Still the viewport shows a different thing than the render. Not that important since it works in the render, but in the viewport I need to invert it again to see it as the render…
Thanks a lot for your time and dedication!