A materialist, capital-r Reality probably exists, but it's not where we as people spend our time. It's not even something we're capable of perceiving or comprehending.
Human perception is the result of four billion years of evolution. It takes sensory input and uses it to build spaces we can understand, in a mental language that *is* our subjectivity. It is not the same construct as a materialist universe built out of atoms or math or whatever.
Our view of reality is one big necker cube.
To think that understanding the materialist world is equivalent to understanding the world we actually live in is a doomed premise.
I don't mean to say "everything is psychological". What I mean to say is that at the end of the day, our qualia are all we have, all that we *are*. Reductivist rationalism is a useful tool but it will never produce all knowledge.
Time is fake as hell, and dimensional space probably is too. We can talk about the universe being built out of math, but that's a human metaphor layer. The idea that the universe is "built out of" *anything* is a cognitive artifact.