I tested this on multiple systems, one with recent hardware and 4x 8tb nas drives +1 boot ssd and an older Xeon E3 based system with 1x 2.5" HDD to confirm the installations not working.
I tried multiple images [I used Rufus and the official truenas scale release for them], but got the same error code on every boot from the installer:
Welcome to GRUB!
error: unknow filesystem.
error: unknow filesystem.
error: unknow filesystem.
error: unknow filesystem.
error: unknow filesystem.
error: unknow filesystem.
error: unknow filesystem.
error: unknow filesystem.
error: unknow filesystem.
grub rescue>
BOTH DID NOT BOOT IN UEFI TO MY KNOWLEDGE!