One of the answers to a similar question regarding gravity concluded that gravity is an "observed effect" of the curvature of space-time. I read this (and other answers) to imply that gravity results from the curvature of space-time and not directly from the masses producing that curvature. Assuming that space-time is massless, where is the $m$ in $F = m a ,$ and without it how can gravity be considered to be a force?
The following answer was provided in response to a related question. It was closest to providing an answer to the question I tried to pose. My apologies for not citing the author. I'm a layman, this was my first question on the forum and I was not able to retrace the thread that led me to that answer.
However, general relativity gives a much deeper picture of gravity as a description of the curvature of space-time, so, in a way, gravity is an observed effect of the curvature of space-time, or, if you like, an observed effect of the distribution of mass and energy.