Resolved! [Please ignore] STM32U5, ThreadX and CMSIS
[EDIT: S'OK, I need to think about this more, but I can't find a way to delete a message so am just marking this as one to ignore]I am just moving from STM32F4 to STM32U5. ThreadX seems to be the thing for STM32U5 (if one doesn't want to use Zephyr)...