There is a bit of discussion here about sole stiffness. One needs to be specific what you are talking about and what PART of the sole you are talking about.
Yes, some hiking shoes have a stiff shank in the middle of the sole (under the arch), but the sole is made to bend under the ball of the foot.
For an clip-less shoe to work really well, it needs to be stiff under the ball of the foot.
I’ve got a pair of mtb shoes that are pretty comfortable to walk around it, but not as much as a non-clip-less shoe.... and they are not the greatest for long days of pedaling due to the flex in them. They are fine for both, but there are compromises.
An alternate suggestion is go with flats with a big platform. That eliminates the need for stiffness under the ball of the foot. And many hiking shoes have a stiff shank under the arch which takes care of that part of the foot. The trick is to fins ones without deep lugs, as the traction pins get lost between them.