  Dark matter can be part of a dark sector with non-minimal couplings to the
Standard Model. Compared to many (minimal) benchmark models, such scenarios can
result in significant modifications in experimental signatures and strongly
impact experimental search sensitivity. In this white paper, we review several
non-minimal dark sector models, including phenomenological consequences: models
explaining $(g-2)_\mu$, inelastic dark matter, strongly interacting massive
particles as dark matter candidates, and axions with flavorful couplings. The
present exclusions and projected experimental sensitivities on these example
dark sector models illustrate the robustness of the growing dark sector
experimental effort -- both the broadness and the precision of existing
searches -- probing theoretically interesting parameter space. They also
illustrate some of the unique complementarity of different experimental
approaches.
