After using Wordpress' Gutenberg-Editor, I find it impressive how easy Users can create complex pages - without need of support from an admin or even developer.
Is there some editor providing available for Plone?
(Please no discussion about Gutenberg. I'm sure ir is far from perfect. My point is: It is empowering the users and taking burden from the admin.)
At the Ferrara PloneConf sprint, we integrated Gutenberg in Gigi which is a Guillotina-based CMS PoC (but it could work on top of Plone RESTAPI).
You'll find some code here https://github.com/guillotinaweb/gigi (just a PoC though), it is all in Angular, so I am not sure it helps a lot, but yes it was working 
I am not aware of any other Gutenberg integration.
Mosaic is a bit similar.
Although using Gutenberg is 'effortless', making 'tiles' is not.
Making theme fragments with Mosaic is very easy and fast.
I made a simple demo once (with some broken fingers, but you get the clue): https://www.youtube.com/watch?v=Kdn8kFeEGkw
We evaluated Gutenberg and also took some inspiration from it when developing the Volto page composition editor.
Gutenberg is pretty neat. Though, it targets advanced technical users that know basic HTML and CSS (at least how it works). You can configure anything you could imagine and that's indeed pretty impressive.
Though, the main use case for Plone is large organisations with lots of editors that do not necessarily posses in-depth technical knowledge. Because of its flexibility, Gutenberg would require lots of editor training, which is a big cost factor for large organisations. Therefore we decided against integrating Gutenberg and we are trying hard to make the Volto page editor as user friendly as possible. Gutenberg is the perfect editor for Wordpress and its main target group: agencies that want to build websites with limited in-depth technical knowledge.
It would be a living hell in Plone if you allow thousands of editors the freedom that Gutenberg gives the user. No way to make sure you have a consistent corporate design, accessibility, same look-and-feel, etc. If you look at university websites or larger websites, you will see what I mean if you look at a site that allows the user even too much flexility in TinyMCE or CKeditor.
My personal advice would be. If you want Gutenberg, use Wordpress. The target groups of Wordpress and Plone are just too different IMHO. You will never end up with a system that satisfies your need.
From a technical standpoint:
Since Gutenberg it is written in React, integrating it into Volto shouldn't be too hard and easier than integrating it into classic Plone.
Though, for Volto we decided to go with DraftJS instead of Gutenberg because of the reasons outlined above as well as the fact that the main work is actually the integration of the editor into the CMS (how to display blocks on the rendering, content browser, resolveuid, etc). Making Gutenberg working in any system is easy and doable in a day or so I guess. Though, then the real work begins...