Edit: The paper is total nonsense. Sorry for wasting people’s time.
It’s utter bullshit from the very start. First, it isn’t true that the Ricci curvature can be written as they do in eqn (1). Second, in eqn (2) the Einstein tensor (middle term) cannot be replaced by the Ricci tensor (right-hand term), unless the Ricci scalar ® is zero, which only happens when there’s no energy. They nonchalantly do that replacement without even a hint of explanation.
Elsevier and ScienceDirect should feel ashamed. They can go f**k themselves.
I do agree the whole paper is bull. Equations (1) and (2) are strictly speaking wrong, but you’d see these kinds of expressions if you are talking informally about these things. (1) should be a Riemann tensor, so its mostly wrong. For (2) it is a bit more general than R=0, since you could have Einsteinian manifolds and can make that redefinition. But yeah, without explaining anything, it’s just nonsense.
Sabine Hossenfelder now has a video about this paper: