Have read about the ORE interrupt problem on STM32F7.
On STM32H7 it looks like the overflow condition prevents setting RNE flag, even in polling mode, without any involvement of interrupts.
With the current H7 HAL driver v 1.5.0, it is very simple: call HAL_UART_Receive; once overflow occurred, it will choke up and won't receive anything else.
A simple remedy is just disable the overflow detection in Cube.
-- pa
/* I like the [awesome] HAL drivers like everyone else ;/
but have to use it until I get time to study the fine manuals and write my own */
