I already tried to do a few things describing in some threads, like change policy, but the option to enable booting from external devices is not there.
What are you trying to boot? Remote exam USB stick? Mac Pro can certainly boot from an external USB device. Make sure the Secure Boot is disabled in the Apple startup security utility https://support.apple.com/en-us/HT208198 Personally, I would not attempt using Mac Pro for the exam as I believe there will be compatibility issues. Let us know if you made it to the compatibility test.
However, booting from USB using Option key is not working. Holding the start buttom drives me to the boot policies setting, but the Allowed Boot Media option is not there as described in https://support.apple.com/en-us/HT208198. Not sure if this is because the MacBook hw/sw version or because any RH policy on it.
Anyone has any solution? other than not using the Mac for the exam, which is the option otherwise
did you create the USB stick correctly? There is an error in the pdf manual, describing the use of dd command for Mac. The home folder is not "home" but "Users". So you need to modify the path. Did you press and hold the ALT key correctly? The USB stick should surely be recognized and visible if it contains a valid bootable system. Also, do not use any USB-C multiport adapter to connect the USB-A type USB stick. Those adapters do not work often.
