The boot log says “spi-nand: Failed to detect a SPI NAND (err = -19).”
It seem like the firmware couldn’t detect the SPI NAND and mount the rootfs on that, so then the kernel panic and reboot. I guess the stock bootloader has done some essential operation to the NAND flash before the firmware boot, without that the firmware couldn’t detect the NAND flash.
Due to the breed is close-source and it not recognize the NAND flash on this router, I think it not possible to use breed boot the stock firmware right now. Perhaps as you said, the only way is to compile a NOR only firmware