I will take a Kantian perspective for granted that there are some aspects of reality that are epistemically unsearchable. I think when it comes to something like cosmology and the origins of the Universe as we know it, especially when we juxtapose it against possibilities of the way the Universe could have been known, these sorts of things are in the category of being epistemically unsearchable. But while the necessary ontology of the Universe is unsearchable, we can at least theorize what a sufficient ontology might be. That is to say (in Kantian terms) a noumenon that would sufficiently bring about the phenomenon. We can do this by working backwards from effect to cause. To begin, I will propose an
a priori ontology that is not controversial. It is inspired by the metaphysics of David M. Armstrong (an atheist), in which he began with the assumption that space-time is fundamental.
If the "initial state" of our Universe is bound to space-time, then I propose that at T0 (before any time has passed), the Universe was confined to a single 3D cube of space. I will also propose that this state is immaterial because no matter can be said to exist at T0. All that exists at T0 is potential energy, which is being expressed as field, which is distributed globally across the single 3D cube of space. For semantic purposes, I will refer to this energized 3D-cube as the Singularity. The Universe we experience has multitudes of material forms, and so the next step in this inquiry will be guided by the following question: how do we get from an immaterial Singularity to a material Universe?
I think the beginnings of an answer to this question can be explored by trying to understand how the Singularity can sufficiently bring about a material state at T1. I think this could be accomplished in a couple different ways. The first way supposes that the Singularity does not expand, and particles simply emerge out of the field. The second way supposes that the Singularity does expand, and this expansion creates a disturbance in the field which in turn results in the emergence of particles. On the first way, I suppose it is possible that an infinite number of particles could emerge until the Singularity reaches a critical mass level until it "explodes" thus causing the expansion of space. However, I wanted to pause for a moment and appreciate how both of these ways seem to entail each other. If particles emerge first and then space expands, so be it. If space expands first and then particles emerge, so be it. It is not important to me at this juncture to determine if the chicken or egg came first. What is important to me is to determine what ontological conditions the Singularity has that sufficiently bring about T1 (however T1 is brought about), so I will assume BOTH ways happen simultaneously, which is to say: particles emerge AND space expands at T1.
By way of analogy, the mechanics of T0 to T1 can be thought of in the same way as cellular mitosis. And so a Universe emerges (begins to exist) because the Singularity is replicating itself. The rate of this replication (logarithmic, linear, or exponential) is unimportant to me; what is important is that it is happening. If the mitosis analogy is apt, then it seems to me that at the bare minimum the Singularity will need to have a self-replication property, a self-organizing (quantizing) property, and a particle-producing property. But what exactly are these properties? If they exist at T0 and T1 and all subsequent intervals of time, then they are eternal (or timeless). If they are not local to any singular cube of space-time, but in fact apply to all cubes, then they are universal (or omnipresent).
But I ask again: WHAT are these properties? Abstract or concrete objects? I do not think the properties are concrete first because they are immaterial, and second because they are mind-independent. In other words, they cannot be manipulated as though they are particles or quantities of energy, nor does someone need to be thinking of them in order for them to exist. This is why I am led to think of them as being abstract, even though they participate with concrete objects (energized 3D cubes of space-time). The next question is whether or not these properties are first-order abstracts or second-order. By this I mean, do the properties instantiate space-time cubes, or do the cubes instantiate the properties? I should think that if the properties did not exist at all, then T1 would not come about; so it is for this reason that I think they are first-order intrinsic properties of the Singularity at T0, which also means they are uncaused.
So to review, the space-time Singularity has the following properties: Self-Replication, Self-Organization, and Particle-Producing. And these properties exist in the following way: Eternal, Universal, Abstract, and Uncaused.
At T1 when the Universe emerges, the game changes somewhat because now we might say the Universe would instantiate second-order properties such as thermodynamics and other physical laws that regulate how space-time cubes will continue to replicate and organize/quantize, and also how new elementary particles emerge from these space-time cubes and begin to organize themselves into various material forms. If these laws are second-order properties instatiated at T1, then they exist contingently, or rather they are contingent upon the Singularity's self-replication before they come into being. But in treating them as contingents, these leads me to consider whether or not they are uniform across all space-time cube. In other words, could space-time cube "Alpha" at T1 have different thermodynamic and physical laws than space-time cube "Bravo" also at T1?
If the answer is YES, then I think we might have a good conceptual model for the many-worlds hypothesis, which says that many different kinds of universes perpetually emerge from an original Singularity. On this model, "Alpha" and "Bravo" become their own Singularities, which then go on to self-replicate and produce "Alpha Universe" and "Bravo Universe" which are separated by a barrier that prevents "Alpha Space" from merging or mixing with "Bravo Space." I am not opposed to this model, but it multiplies entities needlessly to explain the Universe as we know it.
If the answer is NO, then the uniformity of thermodynamics and physical laws become another eternal, universal, abstract, and uncaused property of the Universe as a whole. If not, then uniformity could fail and the Universe would break down into many-worlds. It does not matter to me if many-worlds emerge at T1 or if, say at T2 or any subseqeunt interval, the Universe breaks down and many-worlds emerge. I have nothing against many-worlds other than it being anti-parsimonious. But for argument's sake, at some interval there would have to be uniformity in order for a Universe to have stability, otherwise an infinite number of Singularities would keep forming and breaking down into many-worlds ad infinitum. I doubt such a process would sufficiently yield the Universe as we know it, so at this stage I am comfortable going with the NO answer seeing as how uniformity is a sufficient condition for our Universe.
The diagram below pictures the Singularity at T0, and the Universe at T1 in which the Singularity has replicated, and within the new space-time cubes are new particles.

Theistic Reflection --
1. The simplest elementary particles that I think the Singularity could produce are photons because they have zero rest-mass. The metaphor/poetry of "let there be light" is quite remarkable given this.
2. I believe when one views the properties as a "system" or a "structure" rather than arbitrary components that happen to fit together 'just so' for our Universe to emerge, then the paradigm of digital physics begins to look like a clear winner in terms of which metaphysical vocabulary we should adopt. The reason is because the properties constitute logic, and this logic determines the manner in which our Universe emerged. If so, we can think of God as
the source code of the Universe, or the Logos.
3. If the Source Code determines why and how everything within a space-time cube self-organizes or quantizes, and this in principle can be applied to larger scales that go far beyond a single space-time cube (such as galaxies), then the Source Code is a part of
everything that exists because it is
IN everything that exists.