Perhaps the quest for "a good color space converter" is inappropriate?
Woke up this morning with the thought that a converter is a converter and no more than that. In other words, going from (easy example) XYZ to sRGB is a fixed conversion and, as Andrew said, if it's gonna clip it will. In which case, the question in the OP is not possible to answer in the way that the OP intended. Which is what I believe y'all were trying to tell this obstinate old man
So, if I understand correctly, this raw file will probably not clip (triangle is sRGB):
But the following one could be quite a problem:
The second gamut being that of a sunflower shot in sunlight.
And, if understand further, correct gamut conversion per se
does not include rendering intent which, duh, is what it says it is!
I said earlier that flowers can be troublesome. Here is a typical yellow flower spectral reflectivity:
Looking at the purple line on the graph, that flower is yellow with next to no blue in it.
Here's how ACR (left) rendered my sunflower versus Sigma PhotoPro (right) last year:
Nothing in ACR nor in PSE post could fix those blotches without messing up the image saturation or color balance, whereas SPP and dcraw produced a blotch-free image by magic. I'll stress that it was the blotches that irritated, not the rendered color of the petals (too golden).
Here's the final sRGB image of flower in question and I can't remember how I did it
Thanks to you all for your time and advice,