Godot Engine is one of the most exciting, most advanced free and open source game engines around and it's improving when looking at all angles.
While the continue polishing the current 3.x release series, and working continues on Godot 4 which will bring with it a huge advancement to their 3D rendering with Vulkan, there's a lot more going on.
Recently, it was announced that they've hired Nathan from GDQuest in a part-time basis to go over all of the existing documentation and just make it better. This work was actually funded by someone who donated for this job specifically so that's pretty awesome. Nathan did a video to announce their plan too:
The work being done is of course open to the public, and the Godot documentation itself is also up on GitHub under a creative commons license. Nathan's work has a pretty in-depth in-progress audit up already. Looks like there's plenty of work to be done. Needed work though, as something like Godot needs thoroughly good documentation.