Measurements of electroweak penguin and lepton-flavour violating B decays to final states with missing energy at Belle and Belle II

The Belle and Belle II experiments have collected a 1. 2 ab^-1 sample of e^+e^- B B collisions at a centre-of-mass energy corresponding to the (4S) resonance. These data, with low particle multiplicity and constrained initial state kinematics, are an ideal environment to search for rare electroweak penguin B decays and lepton-flavour-violating B decays to final states with missing energy from neutrinos. Results from b s processes and their interpretation are presented. In addition, we present searches for the processes B K^*0^+^-. Finally, we present our search for the lepton-flavour violating decay B⁰ K^*0^^, and B⁰ K^0S^^ where is an electron or muon.