I just tagged v1.0.0 of nspawn-debootstrap builder plugin for Packer: https://git.sr.ht/~angdraug/packer-builder-nspawn-debootstrap
It will build you an nspawn ready chroot that you can pack up or clone. It provides a communicator interface for Packer's standard provisioners such as shell and chef.
Watch this space for the things I'm going to do with it.
Server run by the main developers of the project It is not focused on any particular niche interest - everyone is welcome as long as you follow our code of conduct!