Hello, coming back after a couple of day of trying, nothing worked. normal flash or initrd flash. nothing seems to be able to write anything to the ssd. but I found a solution finally with trial and error
step 1: acquire pcie to usb and plug the ssd to your host machine
step2: use etcher to burn the sd card image from nvidia website to your ssd
step3: mount the first partition and modify /boot/extlinux/extlinux.conf replace /dev/mmcblk0p1 with /dev/nvme0n1p1 in the kernel command
step3: flash the qspi
sudo ./flash.sh -c ./bootloader/t186ref/cfg/flash_t194_uefi_qspi_p3668.xml jetson-xavier-nx-devkit-qspi nvme0n1p1
step4: boot the jetson and enjoy, (at least for me).
BTW: when you flash the jetson and the script reboots it and wait for ssh to be ready but you get blinking cursor, I checked the serial console and it seems it just booted to the initrd and opened a bash shell and waiting. hope that helps someone