Quantitative finiteness of hyperplanes in hybrid manifolds

We prove a quantitative finiteness theorem for the number of totally geodesic hyperplanes of non-arithmetic hyperbolic $n$-manifolds that arise from a gluing construction of Gromov and Piatetski-Shapiro for $n\ge 3$. This extends work of Lindenstrauss-Mohammadi in dimension 3. This follows from effective density theorem for periodic orbits of $\mathrm{S}\mathrm{O}(n-1,1)$ acting on quotients of $\mathrm{S}\mathrm{O}(n,1)$ by a lattice for $n\ge 3$. The effective density result uses a number of a ideas including Margulis functions, a restricted projection theorem, and an effective equidistribution result for measures on the horospherical subgroup that are nearly full dimensional.