How to unpack the image? And where is the bootloader?

Hi, the official provide the system image

  • Does this image(e.g. ROCK 5B+ Debian(kernel 6.1)) contains the bootloader(TPL/SPL)? I mount this image file, does not find the bootloader, and the partition table(parameter.txt)?

  • For other system(e.g. Android), how can I unpack the image?