It is very possible that you already know what Ubuntu is, but if you are not yet aware is the most popular Linux distribution for a couple of years, which has had many advances at the desktop level, was innovative at the time with the Convergence of devices (already achieved by Windows 10) and now its looking toward the Internet of Things.
If you have experience with Ubuntu and if you are a developer, it is more likely that you will be interested in the official Ubuntu Tutorials site, the last announcement that Canonical has made is about this new site that really looks very interesting, if you do not want Wait more to know it access:
As its description says, it is focused on Snaps and Ubuntu Core, these topics being specific and advanced, but the truth content is very didactic and show you step by step. Although you can also propose topics that interest you here
Ubuntu Tutorials are just like learning from pair programming except you can do it on your own. They provide a step-by-step process to do development and devops activities on Ubuntu machines, servers or devices.
For now, the tutorials focus mainly on building and using snaps and Ubuntu Core.