Measurements of electroweak penguins and $B$ decays to final states with missing energy at Belle and Belle II

The Belle and Belle II experiments have collected a 1.3 ab${}^{-1}$ sample of $e^{+}{e}^{-}\to B\bar{B}$ collisions at $\mathrm{{\rm Y}}(4S)$ centre-of-mass energy. This is ideal environment to search for rare electroweak penguin $B$ decays and notably those involving $B$ decays to final states with missing energy. Results on these datasets of $b\to s{\mathrm{\ell }}^{+}{\mathrm{\ell }}^{-}$ $(\mathrm{\ell }=e,\mu )$, $b\to s{\tau }^{+}{\tau }^{-}$, and $b\to s\nu \bar{\nu }$ transitions are presented.