The future linear 𝑒+𝑒− colliders offer a number of unique opportunities for searches for dark matter and dark sector particles. The collider program itself will offer important capabilities on three frontiers: (i) the precision frontier with measurements at the Higgs factory, (ii) the energy frontier with direct investigations of the scalar sector, and (iii) the intensity frontier with fixed-target and beam-dump measurements. This contribution presents some of the possible experiments, which address various dark sector portals.