It has been proposed that neutrons may have an invisible decay mode into dark matter, due to mass mixing between the DM and the neutron, motivated by discrepancies between the neutron lifetime as measured by decay-in-flight versus bottle experiments. This scenario is highly constrained by neutron stars and dark matter phenomenology. I will describe a model with a subdominant component of elementary dark matter and dark photons, that can be compatible with all the constraints. Alternatively, if the dark matter is a mirror neutron, its mixing with the visible neutron can lead to a novel mechanism of low-scale baryogenesis, starting from an asymmetry in the mirror sector, by neutron-mirror neutron oscillations.