MachinenVM works on macOS (HVF) and Linux (KVM), and is written in Zig, with a TypeScript API and a CLI.
It boots a debian machine in a few 100ms. I think it's at 200ms right now.
You can control the entire machine via TypeScript.
You can snapshot a machine on macOS, and restore it on Linux, and vice-versa.
You can do live mounts from host-to-guest, or static mounts that produce a .img file, you can share ports... this is your microvm