I confirmed to boot of the ‘rock-5b_debian_bullseye_cli_b39.img.xz’ image that was installed to NVMe using the SPI boot loader flashed by the latest normal bootloader of ‘rock-5b-spi-image-gbf47e81-20230607.img’.
The normal bootloader of ‘rock-5b-spi-image-gbf47e81-20230607.img’ probably supports the non-GPT partition image.