I successfully upgraded a SN570 using the standard NVMe firmware update protocol.
On systems with nvme-cli (I ran this on Linux 6.1) you can run this:
nvme fw-download -f 1234WD.fluf /dev/nvmeX
nvme fw-commit -s 2 -a 3 /dev/nvmeX
At least for the SN570 this can be done online, i.e. while the disk is in operation. If that’s not possible (check with nvme id-ctrl -H /dev/nvmeX | grep 'Firmware Activate Without Reset Supported') change to -a 2 and reset the NVMe or reboot.
Please make sure that you only try to flash the correct firmware, the disk should verify it according to the NVMe spec, but I warned you.
