Re: arm64 and isohybrid
the third, zero sized partition "Gap1" gets indeed
produced by libisofs. xorriso command -report_system_area
does not show it, though.
I am investigating. You may assume that this partition
will not be produced in future xorriso versions.
If the "Gap1" partition entry is suspected to disturb anything,
you may create the intended state of GPT by
dd if=/dev/zero of=tmp.iso conv=notrunc bs=1 seek=1280 count=128
(Actually one would have to zeroize the entry in the backup
GPT, too. Its position is 62 blocks before the backup header
block + 256 bytes. The header block number is given by
xorriso -report_system area as third number in line
"GPT lba range". E.g with
GPT lba range : 64 266240 266303
the backup entry of partition 3 is at byte (266303 - 62) * 512 + 256.
Have a nice day :)