Hi,
Just a quick note that support for the LPC55S69 was just merged in, allowing you to use the relatively easy to source LPCXpresso55S69-EVK dev board: https://www.nxp.com/products/processors-and-microcontrollers/arm-microcontro...
Some notes on how to use this board with TF-M are visible here, including how to update the board to use the Segger J-Link firmware image: https://git.trustedfirmware.org/trusted-firmware-m.git/tree/platform/ext/tar...
Samples scripts for building and flashing (which assume the J-Link debug firmware is present) are available here:
- https://git.trustedfirmware.org/trusted-firmware-m.git/tree/platform/ext/tar... - https://git.trustedfirmware.org/trusted-firmware-m.git/tree/platform/ext/tar...
If you find any issues with the board support, you can comment on the LPC55S69 task here: https://developer.trustedfirmware.org/T706
Best regards, Kevin Townsend