As science seeks a unified theory of everything, of reality as a whole, we may need to focus more on contemplating the nature of consciousness and our own self to find the answer.
Where does spacetime come from? Might our mind generate it as a kind of illusion in consciousness? How might we transcend this illusion in contemplation?
Mass-energy and spacetime may not be two separate things, but One thing manifesting itself in two different ways.
General Relativity and Quantum Mechanics are at polar odds with each other, and many physicists are trying to reconcile them in a grand unified theory. Perhaps they are not meant to be unified. Maybe unity is found elsewhere.