I am writing a paper entitled "On static solutions of Einstein's field equations for fluid spheres". I assume there a diagonal stress-energy tensor, $T_{\mu}^{\nu}=diag~\{\varepsilon,-p,-p,-p\}$, but I would prefer to not use the word "perfect fluid" because of restrictions traditionally associated with this notion (energy conditions, equation of state, etc). In my view the left side of Einstein field equations stands for local geometrical properties and the right side for physical properties of spacetime. Under physical properties I understand energy density and mean hydrostatic stress of spacetime itself, with no a priory relation between them as it is usually anticipated by using notion of perfect fluid matter. In other words, $T_{\mu}^{\nu}$ represents physical properties (or state) of spacetime and not matter. I have found only one publication that seems to support such a view. I wonder if someone knows others.
Luciano Combi, "Spacetime is material", arXiv:2108.01712v1