Resolved! LWIP/ V6.5.0. STMH32H735_DISCO (https://github.com/stm32-hotspot/STM32H7-LwIP-Examples) .Rx_PoolSection. (former .RxArraySection) seems not to be guarded by the MPU against cache coherency issues. Is this the right way?
I have compared 2 STMH32H735_DISCO_Eth examples, one built under cube IDE V6.2.1 and a more recent one built with IDE V6.5.0. (thanks to @Pavel A. for providing the reference to the new examples on GIT). The V6.5.0. example moved the Rx_PoolSectio...