“…However, for the case of piecewise smooth geometries such as polygonal and polyhedral domains, sharp local error estimates that exploit the maximal (local) regularity of the solution are not available. Moreover, the analyses of [ 14 , 21 , 27 , 28 ] are tailored to the energy norm and do not provide optimal local estimates in stronger norms, whereas [ 5 ] imposes additional global regularity.…”