How to repack a system.new.dat.br with open source command line tools?

We can decompress a system.new.dat.br and then convert to an img, like this: brotli --decompress system.new.dat.br -o unpacked_system.new.dat sdat2img.py system.transfer.list unpacked_system.new.dat unpacked_system.img mkdir system && sudo mount -o loop unpacked_system.img system I couldn't find anywhere a way to not mount this. I wanted to not mount this because it needs root, and because inside a docker container is hard, and also because I shouldn't need root to repack system.new.dat.br. So, how can I both decompress unpacked_system.img, modify its files, repack it and convert back to .dat.br?