I gave the linked Firmware Utility Script a try on my Purism Librem 13 v2. The script correctly detected the device, and happily flashed the firmware with no reported errors. It informed me that I could restart.
… Unfortunately this soft-bricked the device. The machine still POSTs, and the screen + SD card works. However none of the USB ports work, nor the keyboard. So I don’t have any way to interact with the machine.
Now I’m gonna try and figure out how to prepare an OS image that will kick off the official firmware flash utility in some kind of unattended mode on pty0 at boot.
Just a warning to anyone considering using these builds on their Librem 13 v2!