Dark matter (DM) constitutes one of the most pressing open issues in our understanding of Nature. Candidates with a mass around the TeV scale have been studied for decades and are vigorously explored today, with a clear experimental program. Sub-GeV DM has instead started to receive widespread attention only recently: new motivations for it are being put forward and many new detection concepts are being proposed and assessed. After a summary of the status of sub-GeV DM, I will discuss its high-energy fluxes that necessarily reach us on Earth, and the novel DM detection techniques that they open today, with existing experiments. In particular I will present searches, at large neutrino detectors (like Super- and Hyper-Kamiokande, JUNO and DUNE), for DM i) upscattered by cosmic rays and ii) produced in atmospheric showers. These will result in the strongest existing limits on a wide class of sub-GeV DM models.