Early stage software development is tricky, but not unique.
I think someone who’s done the role before would be more valuable than someone smart.
They are also easier to find and screen.
I'm actually the type of person that you'd want, but I'm not looking for work.
You want someone that can deliver product, and that type of person does not grow on trees. Experience will be the main factor. Maybe not as old as I am, but I have known a lot of folks in their late thirties and early forties, that have the requisite experience. These folks are the ones that are finding themselves frozen out of the job market, these days, and would probably be open to the relatively unstructured environment of an early startup (when, previously, they were not, but mortgage payments have a way of opening us up to compromise).
Unless, of course, your "product" is the company, itself. In that case, someone that plays to investor preconceptions may be more along the lines of what you want.
Where do you usually look for this kind of ppl?
After that, your usual sources should be fine. If you need help with ops, find someone that has done it before.
I would be very specific in your job application.
Don't say, "We are looking for an ops expert." Say, "We are looking for an ops engineer with experience deploying .NET core web applications to azure." From there, you should be able to verify if they have done it.