Koszul duality for observables in holomorphically twisted AdS/CFT

Let $\mathbb{X}$ and $\mathbb{Y}$ be field theories, and let $\mathsf{Obs}_{\mathbb{X}}$ and $\mathsf{Obs}_{\mathbb{Y}}$ denote their observables. For an $\mathbb{E}_n$-algebra $A$, write $\mathbb{D}(A)$ for its Koszul dual. Costello–Paquette–Costello–Li conjecture. The holomorphically twisted version of AdS/CFT duality gives an example of Koszul duality for observables. The supplied text identifies this as an open problem, but does not state a more precise equivalence or specify the corresponding theories and observables, so the mathematical content of the conjectural example remains to be clarified.