Its also possible to build the Proxmox container directly with nixos-generators, with the added bonus that you can configure the VM specs in nix as well

https://nixos.wiki/wiki/Proxmox_Virtual_Environment

As far as I can tell that is what Hydra is doing, and yet you still need to jump through the rest of the manual hoops… So I’d rate those docs as outdated.

Yeah, if you use the VMA approach, you’ll need to manually import the VM via UI or CLI.

I wonder if a combination of nix-generators and Terraform or Ansible would work..

OrbStack (proprietary WSL and Docker Desktop clone for macOS with a GUI management application, very well made) uses LXC for all its 'Machine' guests, including NixOS.

Consequently, I can say that I use NixOS under LXC on aarch64 almost every day at work. :)

It runs perfectly well under LXC! NixOS also works well under WSL2 on Windows, though setting that up takes more footwork. If you're thinking about playing around with NixOS, virtualizing it— whether hardware or OS virtualization, whether on your laptop/desktop or in your homelab— is a great way to go.

Neat. Been meaning to try nixOS but couldn't figure out the LXC part

There is now also a project to run proxmox inside of Nixos

https://github.com/SaumonNet/proxmox-nixos