bhyve
For some reasons I needed a Linux installation on my NAS. byhve is a lightweight virtualization solution for FreeBSD that makes that easy and efficient. However, the CLI of bhyve is somewhat bulky and bare making it hard to use, especially for the first time. This is what vm-bhyve solves - it provides a simple CLI for working with virtual machines.
The only requirement seems to be VT-x CPU support or whatever it may be called on AMD CPUs and ZFS as a file system.