Hi Chris, Seems like El Torito boot information is not present in the ISO file (for Debian). Not sure if this was omitted out on purpose (because I can see that it is being added for x86 in the debian-cd repo in salsa). According to qemu docs, El-Torito boot information is required for qemu to boot the ISO (https://qemu.weilnetz.de/doc/6.0/system/s390x/bootdevices.html)
Will update further if I find anything else. Thanks, Pranav

