stm32l467-DISCO:nsh Serial not working 100% with permutations of HW FC (both on chip and GPIO) /DMA

It does work correctly with GPIO flow control. :+1:
It drops chars with HW flow control (on chip). :-1:
It also drops chars with DMA with GPIO flow control. :-1:
With DMA the test app hangs on close. :-1:

I noticed the DMA arrangement is not the same as F4, F7, H7, I suspect this is the root cause of the DMA issue.

The character loss may be fact that one octet can be in flight inbound and does need to be received, even after RTS is de-asserted. Another observation is the pin is named differently from the STM32F4...