Nebula is great - super simple to set up and get started if you have a VM to use as a lighthouse. Lots of cloud providers free tiers are have enough resources to host a lighthouse as well.

Certificate management is its one weakness at the moment. There are a growing number of projects floating around attempting to solve that though:

- https://github.com/unreality/nebula-mesh-admin

- https://github.com/b177y/starship

- https://github.com/symkat/MeshMage

Plus im sure defined networks has their own solution in the works as well.