Trying to run a live Ubuntu USB stick

I am trying to diagnose a power issue on a Framework 16. As part of the testing, I would like to start the laptop on Ubuntu rather than booting from the internal Windows 10 drive. I have generated a live distribution USB drive and tested it on another (Framework 13) computer and it is working. I have changed the BIOS on the Framework from boot order ‘auto’ to boot order ‘first’. Curiously, the boot manager currently only sees the Windows drive and not the attached USB drive.
Anyway, out of a number of boot attempts, most ignore the USB drive and boot into the Windows internal drive. On two occasions the computer did actually start booting from the USB stick but in both cases the boot did not complete and the system crashed.
I am curious if anybody has managed to ever boot a Framework 16 from a USB Ubuntu Live stick.
BTW, I did make a second USB stick using a different source file but with the same results.

I’ve booted from a USB stick, in order to install Ubuntu.

I don’t remember the exact settings, and my FW16 isn’t at a point where I want to reboot it at present, but I believe all I had to do was turn off Secure Boot and spam the F12 (?) key when it was starting up, and it gave me a menu of the available drives to boot from, including the USB stick.

(There was a Windows boot drive when I installed Ubuntu.)

Update:
It would appear that I have encountered a somewhat defective USB stick which is now completely dead. I will need to acquire a new stick and run more tests but this will take a few days.