HACK - Not recommended for production !
wget http://archive.zfsonlinux.org/debian/pool/main/z/zfsonlinux/zfsonlinux_8_all.deb
dpkg --unpack zfsonlinux_8_all.deb
vim /var/lib/dpkg/info/zfsonlinux.postinst
Change line 23 to (simply replace Debian with Devuan)
if [ "x$id" = "xDevuan" ]; then
Save and quit vim.
dpkg --configure zfsonlinux_8_all.deb
gpg --quiet --with-fingerprint /etc/apt/trusted.gpg.d/zfsonlinux.gpg
apt-get update
apt-get install debian-zfs
Reboot and have fun !