isc-dhcp* packages that include the generate() operator are available for
Debian Stretch through the following repository:
  URL: https://xavier.kindwolf.org/deb/
  GPG key: https://xavier.kindwolf.org/deb/conf/xavier.pkgrepos%40kindwolf.org.gpg.key

How to use it?
# apt install apt-transport-https
# wget https://xavier.kindwolf.org/deb/conf/xavier.pkgrepos%40kindwolf.org.gpg.key -O /root/xavier.pkgrepos@kindwolf.org.gpg.key
# apt-key --keyring /etc/apt/trusted.gpg.d/xavier-kindwolf.gpg add /root/xavier.pkgrepos@kindwolf.org.gpg.key
# cat > /etc/apt/sources.list.d/kindwolf.list <<EOF
deb     https://xavier.kindwolf.org/deb/ stretch main
EOF
# apt update