The problem is the bash function dep_add_modules_mount in /usr/share/initramfs-tools/hook-functions which doesn't handle zfs.
By adding "MODULES=most" to /usr/share/initramfs-tools/conf-hooks.d/zfs, the error goes away.
I'm still having trouble getting kdump to actually create a crash dump with ZFS on root.
The problem is the bash function dep_add_ modules_ mount in /usr/share/ initramfs- tools/hook- functions which doesn't handle zfs.
By adding "MODULES=most" to /usr/share/ initramfs- tools/conf- hooks.d/ zfs, the error goes away.
I'm still having trouble getting kdump to actually create a crash dump with ZFS on root.