Does an infalling observer see vacuum at an old black hole's horizon?

For a black hole past the Page time (when half the initial Bekenstein-Hawking entropy has been radiated), determine whether a freely falling observer crossing the horizon finds the local vacuum (mode occupation near zero for wavelengths much shorter than $r_s = 2GM/c^{2}$) or high-energy quanta up to the cutoff (a firewall). An answer specifies which assumption of the Almheiri-Marolf-Polchinski-Sully argument fails (unitary evaporation, local effective field theory outside the stretched horizon, a black hole that a distant observer describes as a quantum system with $\exp(S_{\mathrm{BH}})$ states, or a smooth horizon for an infalling observer), in a framework where the computation is controlled.

A calculation in a UV-complete theory, such as an evaporating AdS black hole with a known dual, of infalling observables at the horizon after the Page time.