I do away with substance in my conception of process metaphysics.
The closest analog might be the reality of generals, especially the general habits to which nature reliably conforms. That is, there does not exist one thing, say in the instance of materialism claiming that all is matter, but instead there are three general modes of reality: possibility, existence/energy, and law or habit. These ontological categories are generative and modal rather than substantial, so it cannot be said that there is one kind of existence that is primal, e.g., the material, but rather that reality consists in natural things that resist other things in individually characteristic ways. I just gave an analogous definition for "material existence," which in this case is not the inherence of form in matter.
If I were accused of neo-neo-cryptic-Aristotelianism, that would not entirely be false ... if Aristotle became half Heraclitus!