Proxmox VE is a completely open-source platform for all-inclusive enterprise virtualization that tightly integrates KVM hypervisor and LXC containers, software-defined storage and networking functionality on a single platform. As it is using KVM you can run FreeSBC on Proxmox. You can use KVM image or iso file. Please check following link for Proxmox Installation How to instal FreeSBC on Proxmox VE