GNSS does in fact work fairly well even in conflict zones, but I'm not sure why you're trying to make this point. Everything is vulnerable to some level of warfare and civilian infrastructure is almost never designed with the expectation that it'll operate in a conflict zone. Are you suggesting we individually airgap all the networking equipment with local atomic clocks behind 10m of specially reinforced concrete instead?

Even the most secure civilian facilities (data centers) are fine sticking 2-3 receivers on the roof and calling it good.