I just purchased an Ubuntu 16.04 droplet. I want to setup my own firewall with nftables. I installed nftables successfully. I can start the nftables.service manually, but when I try to enable it to start at bootup with:

sudo systemctl enable --now nftables

I get the following error:

update-rc.d: error: nftables Default-Start contains no runlevels, aborting

What is this? Is it some kind of old-school Sys V error?