My understanding is that from General Relativity (GR) mass carrying particles (and other energy-momentum) curves space-time, and that curvature is what we understand as gravity. I'm aware of there needing to be an exchange particle due to quantum mechanical (QM) representations, but have not been convinced how they work.

I wonder if the Higgs particle could be a candidate for the force carrier in the QM representation of GR (e.g. the resulting higgs field interacts with and causes space-time curvature instead of energy-momentum doing it directly). That is speculation on my part from a lay-person perspective, so could be completely wrong.