The "universe out of nothing" is, essentially, pseudoscience.
There are some GR problems. Namely, the evolution of the universe starts with a singularity. If one closes the eyes, this may be interpreted as "simply one point", or, even worse, once there is nothing before the singularity, "the universe is created out of nothing". Nonsense. The theory we have simply fails in the early universe.
That means, we have, in the very early universe, an initial state with properties where our theory is unable to make any meaningful statements. This initial state is not at all a point, but the same infinite universe. Quite homogeneous, but nonetheless not exactly homogeneous, but locally inhomogeneous in the same way as our universe today.
GR has also some problems with local energy and momentum conservation. As a result, one can claim that there is no energy conservation. But this not at all based on some real physics which would tell us that energy is not conserved. Instead, even in GR we have conservation laws, only the physical interpretation of these pseudotensors fails in the standard spacetime interpretation - roughly, it would depend on a choice of a preferred frame, which, accorting to the spacetime interpretation, does not exist. So a local energy density does not exist too, it is not allowed to exist by the metaphysics of the interpretation. Does it follow that we can now violate energy conservation and get even the whole universe out of nothing? Of course, not, only in pseudoscience.