The new version FAI 5.8.1 now generates the configuration file for Ubuntu's netplan tool. It's a YAML description for setting up the network devices, replacing the /etc/network/interfaces file. The FAI CD/USB installation image for Ubuntu now offers two different variants to be installed, Ubuntu desktop and Ubuntu server without a desktop environment. Both are using Ubuntu 18.04 aka Bionic Beaver.
FAI 5.8.1 also improves UEFI support for network installations. UEFI boot is still missing for the ISO images.
The FAI ISO images are available from [1]. The FAIme build service [2] for customized cloud and installation images also uses the newest FAI version.
[1] https://fai-project.org/fai-cd/