Abstract: Rich dark sectors provide an attractive framework for addressing several puzzles in particle physics and cosmology within a single model. In this talk, I will present a simple sub-GeV dark-sector realization featuring a dark matter candidate, a light scalar mediator, and an extended neutrino sector. I will show how the model can reproduce the observed relic abundance, generate light neutrino masses, and satisfy cosmological constraints. I will then discuss its phenomenological implications, focusing on neutrino signals that could be probed by current and future neutrino telescopes.