Terao's minimal-degree conjecture for free line arrangements

Let ${\mathcal A}$ and ${\mathcal B}$ be line arrangements with isomorphic intersection lattices

$$L({\mathcal A})\cong L({\mathcal B}).$$

For an arrangement ${\mathcal A}$, let $r({\mathcal A})$ denote the minimal degree of a Jacobian relation. Terao's minimal-degree conjecture. If ${\mathcal A}$ is free, then

$$r({\mathcal A})=r({\mathcal B}).$$

This is presented as the line-arrangement reformulation of Terao's freeness conjecture and is open; the intersection lattice does not determine $r$ for arbitrary line arrangements.