Non-Semisimple TQFT's and BPS $q$-Series

We propose and in some cases prove a precise relation between $3$-manifold invariants associated with quantum groups at roots of unity and at generic $q$. Both types of invariants are labeled by extra data which plays an important role in the proposed relation. Bridging the two sides – which until recently were developed independently, using very different methods – opens many new avenues. In one direction, it allows to study (and perhaps even to formulate) $q$-series invariants labeled by spin$^c$ structures in terms of non-semisimple invariants. In the opposite direction, it offers new insights and perspectives on various elements of non-semisimple TQFT's, bringing the latter into one unifying framework with other invariants of knots and $3$-manifolds that recently found realization in quantum field theory and in string theory.