Hello,

as in an archived bug:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=735496

this was again the case on my fresh debian buster install

in short (when using keyctl script in crypttab):
$update-initramfs -u
fails with
E: /usr/share/initramfs-tools/hooks/cryptkeyctl failed with return 1

solution as before:
install keyutils

hth,
Wim