Unfortunately not... TurnKey is primarily run as a VM and our hardware and alternate filesystem support is sadly lacking. Currently our installer only supports legacy BIOS (i.e. no UEFI and/or secure boot support) and ext4 (with or without LVM).

We do have plans to rebase on the default Debian Installer (we currently provide our own minimalist installer, based on components of the default Debian installer). Once we do that, anything supported by the default Debian install should be supported. Unfortunately I do not have a timeframe for when we might implement that. I'm hoping within the lifetime of the v18.x release, but I can't yet commit.

Having said that, if you're handy with Linux, you could just partition and format your disk(s) with ZFS (or any other supported filesystem) using a live distro (that does support ZFS). Then unsquash the root squashfs from the relevant TurnKey ISO and copy it to the fresh partition. Once the files have completed copying, you'll also want to install the zfsutils-linux package (chroot into the newly copied system and install the package via apt).

If that seems a bit too hard, and your main purpose is for data redundancy, then you could do a default install to a smallish ext partition and move the relevant data to ZFS partition.

Finally, unless your hardware is particularly old or low power, or you anticipate particularly high traffic and/or resource usage, personally I think installing to hardware is such a waste of resources. Personally I use Proxmox VE (which incidentally does support ZFS OOTB) - more info here or on wikipedia. It's a Debian based Hypervisor that supports both "proper" VMs (via KVM) as well as LXC (light weight Linux Containers- a little like Docker, but intended for a complete OS). TurnKey LXC templates are available to download via the powerful web UI. Even if you only plan to run one server, the flexibility of running it on a hypervisor makes it my preference over hardware install any day.

So bottom line, if you want TurnKey on ZFS, then you'll either need to wait until we support it, configure it yourself (ask for more details if you're interested in my earlier suggestion) or leverage ZFS via Proxmox,

Sorry that I don't hve anything better for you at the moment...