Semi-inclusive deep-inelastic scattering (SIDIS) is a well-established tool to study transverse momentum-dependent parton distribution functions (TMDs) and fragmentation functions. With the CLAS12 detector at Jefferson Laboratory (JLab), precise, multidimensional measurements of cross sections and asymmetry observables become possible in the valence quark regime. The implementation of different unpolarized as well as longitudinally and, in the future, transversely polarized targets in combination with a polarized electron beam provides access to all structure functions of the SIDIS cross section into unpolarized hadrons, while the large acceptance of CLAS12 allows a wide kinematic coverage. Furthermore, different electron beam energies can be used to perform a longitudinal-transverse separation of the SIDIS cross section. This contribution will provide an overview of the ongoing activities in the field of single-hadron and di-hadron SIDIS. A special focus will be set on the extraction of the structure-function ratio $F_{LU} ^{sin\phi}/F_{UU}$ for all three pions and charged kaons over a large range of $Q^2$, $x_B$, $z$, and $P_T$ .