[whazor]

There is also https://microvm-nix.github.io/microvm.nix/ if you want increased isolation.

[sshine]

I can recommend MicroVM.nix, since it allows for multiple VM runtimes like QEMU, Firecracker, etc.

There's also nixos-shell for ad-hoc virtual machines: https://github.com/mic92/nixos-shell