This is based on https://www.hungred.com/how-to/setup-openvpn-on-proxmox-lxc/
- To enable TUN interface we need to add some configuration information to the LXC config file
It can be done in /var/lib/lxc/xxx/config or in /etc/pve/lxc/xxx.conf where xxx is container number.
2. After adding - restart container
3. Now login to container as root and execute some commands to create interface
After this - just restart container and it should all be ready to go.