What are the solutions for the React Block Builder?

Question

React

Hello.
I saw a React block constructor at Chulakov's studio.
Does this exist for free?
I know they use Strapi.
Yes, and the block constructor is similar to the Strapi admin panel:

Screenshot

Answer 1

For custom CMS I chose - Editor.js
For WordPress, as it turned out, Gutenberg can do this.
And as for Chulakov's Studio, they answered me like this: "self-written content editor on Vue.js".

Answer 2

You can strapi and use
Here is an example manual