Iirc, LIGO confirmed that there was no leakage from/to other dimensions, hence that we can safely reason (at least on this problem) within our current 4D manifold.

It doesn't (cannot, really) state about the possibility that our universe, though self-contained in 4D, might be floating in a higher-dimensional space, like a 2D surface would float in 3D (and could be internally very consistent).

String theory, by the way, might not prove or disprove any of that (see my other reply to parent).