I am a longtime LXC/LXD user.

I've used many different Mesh VPN solutions (vpncloud, nebula, wireguard etc)

All are relatively complex to configure or update which hinders adoption.

Recently, I found Hyprspace:

https://github.com/hyprspace/hyprspace

This is unique because you don't have to configure or add anything to the LXD Host.

Install Hyprspace in any/all LXD containers local or remote.

Edit each LXD container's /etc/hyprspace/hyprspace.yaml (see the GitHub README.md) and change the IP

(10.x.x.x, 172.16.x.x or 192.168.x.x)

In the PEER section of each YAML add the:

ID & IP from the Hyprspace YAML of some local/remote LXD container's Hyprspace YAML you want "this" LXD Container to PEER with.

In each YAML's peer section, add as many PEERS as you want.

Obviously, you could automate much of this configuration in lots of ways.
cloud-init, Ansible etc etc

When you execute the command to bring up each Container's Hyprspace Interface...

All LXD containers will connect using the Hyprspace IP network you assigned in each YAML.

Connection usually takes 20-60sec

Afterwards, each local/remote LXD Container will be directly interconnected in a fully encrypted MESH VPN.

I've tested w LXD Host servers on Digital Ocean, Hetzner cloud in Germany & my local servers and performance is great and config is stupid simple.

Anyway wanted to fyi you in case it helps your project.

A closely similar project to Hyprspace architecturally (IPFS, DHT, libp2p) but which also has an API so it can be integrated is EDGEVPN:

https://github.com/mudler/edgevpn

Brian