User DZS has directed me to a paper which provides a relativistically covariant ontology for QFT! Consistent histories already had this, but the histories there can be arbitrarily sparsely specified. This ontology, "space-time state realism", goes to the opposite extreme and it does so very ingeniously. It uses the "Heisenberg picture" of QFT rather than the "Schrodinger picture". The Schrodinger picture is the usual one in which the state vector evolves in time and the operators do not. The Heisenberg picture is usually described as using a state vector which doesn't evolve in time and operators which do; but the important fact, for the purposes of interpretation, is that the operators are associated to space-time points and so form a manifold-like set that can be relativistically transformed.
Operators are not yet states, however. What these authors (Wallace and Timpson) do, is to define a Hilbert space for an arbitrary space-time region, and then a way to construct a state in that Hilbert space, using data about how the field operators in that region behave with respect to the unique "initial" state used in the Heisenberg picture. So in their ontology, absolutely every space-time region and subregion (every open set, maybe? haven't gone over the details) has a quantum state attached, in a way that is consistent across regions. It's very clever, and it's just enough overkill to guarantee that the true ontology is almost certainly hiding somewhere in there.
Permutation City is an awesome novel that was written in 1994. Even if the author, Greg Egan, used a caricature of this community as a bad guy in a more recent novel, his work is still a major influence on a lot of people around these parts who have read it. It dissolves so many questions around uploading and simulation that it's hard for someone who has read the book to talk about simulationist metaphysics without wanting to reference the novel... but doing that runs into constraints imposed by spoiler etiquette.
So go read Permutation City if you haven't read it already because it's philosophically important and a reasonably fun read.
In the meantime, if you haven't then you should also read A Fire Upon The Deep by Vernor Vinge (of "singularity" coining fame) and then read Eliezer's fan fic The Finale of the Ultimate Meta Mega Crossover which references both of them in interesting ways to make substantive philosophical points and doesn't take too long to read.
In the comments below there will be discussion that has spoilers for all three works.