Hi javirdzh, yes, this thread has been very quiet.
To me, it looks like the problem is that not all the necessary HAL libraries for the STM32H7 chip are ported to the Arduino platform yet. Furthermore, I read somewhere that the USB connector on the portenta uses the HS USB, which is not supported by the STM32 bootloader within the STM32Cube ecosystem, making it difficult to connect to the Portenta in other ways than the Arduino platform. I am not sure if that is correct, but it might explain why I didn't get anywhere with the STM32CubeProgrammer on the portenta although it should, in theory, support the STM32H7 chips and high speed ADC.
I had some limited success trying to port the code from this tutorial, using the STM32CubeProgrammer to generate code for the STM32H747XI:
but I haven't got the higher sampling rates going.
Porting the code in this way is too time-consuming for me, not having a lot of experience. While waiting for the portenta to get access to all the necessary STM32H7 HAL ADC libraries, I have ordered a Nucleo-144 board with a comparable H7 chip to at least be able to test the ADC abiities and settings without the connectivity and micropython abilities of the portenta.
Good luck and please keep us posted on any progress!