GP ARM64 is a manual download from Palo CSP anyway, so would just need another product in PMPC to use for the manual repo side of things.
Architecture is easy to detect natively on the device via the below reg keyvalues:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\Environment\
PROCESSOR_ARCHITECTURE = ARM64
x86/AMD64 variants of GP do not work on ARM64