Thank you Tesla,
just to clarify, I am trying to connect to the board via USB cable.
Parity even doesn't make a difference and I struggle with finding out how to set BOOT0 on the Portenta H7 board. I came across this post:
https://community.st.com/s/question/0D53W00000ElW5DSAV/stm32h747-how-to-start-the-system-boot-loader-via-software
including a comment by TDK:
"Looks like the USB connector on that board is using the HS USB which is not supported by the STM32 bootloader."
to which reefwing replied:
"The Portenta can do both HS and FS USB however Arduino devices have a proprietary USB VID/PID"
Do the errors I get make sense in this context? Any idea how to connect to the board using FS USB?
However, returning to my initial question, my goal is to achieve the advertised ADC rates for this particular board. In the meantime, I have found a promising tutorial at https://deepbluembedded.com/stm32-adc-read-example-dma-interrupt-polling/ which uses the STM32CubeMX to generate some background code. Most of the hal libraries have been ported by the arduino people, so my next approach would be to generate the setup code (main.h and Init functions) for the STM32H747XI (thank you @reefwing !) and incorporating that using the arduino IDE.
If this approach works, I will not need to use the STM32CubeProgrammer to connect to the board. I'll post any progress here.
Many thanks for your help!
