The abundance conjecture for very basic slc-trivial fibrations

Let $f\colon (X, B_X) \to (Y,D)$ be a very basic slc-trivial fibration, where $D$ is the divisor in its structure decomposition. The abundance conjecture. If $D$ is nef, then $D$ is semi-ample. This conjecture is presented as an immediate consequence of the lc-conjecture under the assumption that abundance holds for log canonical pairs; its general status is not resolved in the source.