I ran into a very non-descriptive error running the syzkaller create-image.sh script via easylkb, which relies on debootstrap under the hood:
I: Extracting passwd...
I: Extracting perl-base...
I: Extracting sed...
I: Extracting sysvinit-utils...
I: Extracting tar...
I: Extracting tzdata...
I: Extracting util-linux...
I: Extracting zlib1g...
127
[!] Error running create-image.sh.
After some strace debugging it turns out that debootstrap was missing zstd, which as it were was patched on unstable just a few days ago. Mentioning it here in case anyone else runs into it.