After a few requests, here is a tutorial on how to create dedicated servers with Godot Engine. In this tutorial I show how to obtain that through a single Godot project, instead of using one project for server and another project for client.
Note that there is a little bit of the synchronization code to showcase the proposed code architecture in practice, although this part of the tutorial uses my Network Addon.
The dedicated server tutorial can be found here.
Happy forging!