  We study the symmetric monoidal 2-category of finite semisimple module
categories over a symmetric fusion category. In particular, we study
$E_n$-algebras in this 2-category and compute their $E_n$-centers for
$n=0,1,2$. We also compute the factorization homology of stratified surfaces
with coefficients given by $E_n$-algebras in this 2-category for $n=0,1,2$
satisfying certain anomaly-free conditions.
