Assignment problem with no cost
Let $P$ be the set of people and $\mathcal{S}$ be the modified multi-set of subsets. By checking if an $\mathcal{S}$-saturated matching into $P$ exists (i.e. Hall's condition) you are indeed finding a diverse group. If you are checking that some group $P$ is a putative solution the procedure is the exactly the same.

This can be done quickly via the Hopcraft-Karp algorithm (as you don't have weights over edges) or by implementing this as a Max-flow LP and using a solver. I'm willing to bet the solvers will work much faster in practice.