Lumpio: thejpster Thanks! This is the C++ library that also provides bootloader for execution from the QSPI flash, so it shall be possible I think. https://github.com/electro-smith/libDaisy/tree/master/core
This is the MCU that is on the board: https://www.st.com/en/microcontrollers-microprocessors/stm32h750ib.html
I have an ST-Link debugger if this was the question, I don't know how it would handle the erase of the external flash.
I hoped this is a fairly common problem, so maybe I was wrong? :-)