How can I unlock & flash QSPI not using l4t_initrd_flash.sh?

Bought 32 units of fresh Orin Nano 8G last year

all of them assembled to custom carrierboard and flashed bsp based on 35.5

Why I mentioned 35.5 : Due to UEFI assertion issue on ~ 6.1 (Assertion issue in UEFI during boot) few devices entered fault state, customer complained

so I need to reflash the QSPI - 32 devices, with bug fixed binary