JetPack is a front end to the installer software, and does not take part in a running system.
JetPack itself requires x86_64, it cannot run on other architectures (it is a foreign architecture to a Jetson). The software which performs an actual flash is x86_64 binary code, and cannot run on anything but a desktop 64-bit Linux PC (JetPack additionally requires a particular version of Ubuntu on the host, the driver flash software has less restrictive requirements when run by command line instead of the JetPack front end).
Since installer software creates a loopback image of the entire file system as a temporary file during flash, any attempt to run a flash from a Jetson would require the entire eMMC just for a temporary file…and then many GB beyond this for other files, such as the entire operating system from which the temporary file is created. You would have to not only port the flash software to run from aarch64 (not possible), you’d also have to put a very large (relative to existing eMMC) hard disk on the Jetson.
The only possibility for JetPack is to run from an Ubuntu desktop host. Running just flash can only work from a 64-bit Linux host.
NOTE: A host might need in excess of 25GB of free space to put in JetPack.