Going to declare here that I am a complete non-believer, and I do think its unfair for you to ask what evidence and then reject the answer, but on the other hand many seem to be thinking science from the 1600's - which isn't unreasonable, given the school narrative.
I am unclear why you keep referring to the physical and spiritual as if this is a defined separation - scientific proof also keeps on being mentioned, but am not aware of any scientific proofs to demonstrate a hypothesis.
Mathematics is not part of any physical domain, it is abstract. It defines the arguments that lead to undeniable proof - including proof of a negative. Anything else is simply not proven - like most theories, maybe this is the ultimate spiritual plane.
Religion/Science/People look to provide ways to explain and then harness those explanations in new contexts - the explanations don’t need to be 100% accurate, nor have reasoning why, but do need to be universal within our extent of experience. I don’t think religion is any different to science in this context - religious belief and theoretical science does the same thing, proposes theories and interpretations that humans can understand, and then aims to use those explanations.
Scientists with firm beliefs have also been caught in the same way as believers in religions, believing so much in their own theories, that they cannot accept it when the (highly probably) truth is that they are wrong is discovered - or don’t accept that without some evidence, a theory is just that - a curiosity, but useless in its own right. Personal investment is very strong.
On the other hand, something really stands out - when people use non-religious theories that have no evidence, the good theories lead to discovery of a new part to reality, advance understanding, and achieve a change that nobody can deny. You may not understand special relativity and quantum mechanics (or you may), and nobody knows why they should work as well as they seem, but you have to accept that GPS does work, and could not unless those theories were a good approximation to the truth.
On the other hand, nothing has been shown to be achieved by a belief in god - as a concept the theory doesn’t seem to offer anything beyond the absence in god can provide. This doesn’t mean that its wrong, it could simply be too subtle for the difference to be noticed, like many other theories over the years - but it also means the belief in the theory or not makes no difference.
I would suggest that most things that have previously been attributed to god have now been demonstrated to be attributable to mechanisms that the god theory is not required to explain. Although any theory can be revised, a theory that offers nothing in positive evidence, but has many claims demonstrated to be incorrect does taint those who then try to claim the same theory or derivative of still applies. This is the opposite of a newer model becoming more accurate than an existing good model.
I might be going too far, but would suggest it is reasonable that it should be accepted by all that some god (once clearly defined) theory may be a plausible theory, but it also shows quite a lack of critical thinking to not accept that a theory without evidence demonstrating any difference whether true or not, and especially one which has had so many claims showed to be false should be given much weight, and then used to provide a path through life.
Why not join the thinking proven to move understanding forward rather than follow in the footsteps of those whom have been continuously been demonstrated to be wrong? It doesn't mean eventually there might not be something there, but playing the lottery seems to have much better odds.