Thanks Alexey,
I was suspecting it was something like that.
Maybe you have in your magic luggage an already existing "pythonesc" formula for this kind of calculation : Axe of the mesh compared to the North (0°), resulting in a rotation degrees to apply on the Bbox?
As a workaround, i use a mix of your both scipts"BBox to CRS" and "CRS to BBox", see attached script.
Thanks for any suggestion for improving it, escpecillay with the magic formula :-)
Best regards!