User permissions/feature limitations of the native zfs smbshare service on linux

ZFS on Linux uses the usershare feature of samba. So to make this work, you have to enable this in smb.conf by defining a directory for storing the usershare definitions

[global]
; directory for storing the usershare definitions. permissions
; of the directory govern who can use this.
usershare path = /var/lib/samba/usershares
usershare max shares = 100
usershare allow guests = yes
usershare owner only = no

and you have to actually create the directory

mkdir /var/lib/samba/usershares
chgrp foo /var/lib/samba/usershares
chmod 1770 /var/lib/samba/usershares

now restart smbd.