Nhat Huynh Van

<blockquote>
It’s hard to change if you love something!
</blockquote>
I’ve been using the original/classic editor for over 10 years now and the experience has always been 100% smooth and the original Visual Editor was awesome. 
I like to keep that to myself and I’m sure there are some people like me who like the classic, easy to use and simple thing.
This plugin disables the new Gutenberg Editor (Block Editor) and replaces it with the Classic Editor. 
The Disable Gutenberg plugin restores the classic (original) WordPress editor and the “Edit Post” screen.
Features
<ul>
<li>Classic Editor</li>
<li>Disable Block Widgets and restore Classic Widgets</li>
<li>Enable/disable frontend Gutenberg stylesheet</li>
</ul>
<blockquote>
Works same as Classic Editor plugin, but lightweight, simple and super fast
</blockquote>
Easy to Use
<ul>
<li>Super simple</li>
<li>Clean, secure code</li>
<li>Built with the WordPress API</li>
<li>Lightweight, fast and flexible</li>
<li>Works great with other WordPress plugins</li>
<li>Focused on flexibility, performance, and security</li>
</ul>

Relive Classic

Plugin Relive Classic is help you use editor, widgets in classic style and disable Gutenberg.

Sumit Singh

Classic Widgets with Block-based Widgets allows you to use both widgets screens at the same time. 
Sometimes, you need to use the classic widget screen for some of the widgets without permanently disabling the block-based widgets. With this plugin, you can access the Classic Widgets screen in <code>Appearance > Classic Widgets</code> and the block-based screen at the usual place in <code>Appearance > Widgets</code>.
NOTE:- 
This plugin uses WordPress filters to create a new classic widget screen. That means it will work as long as WordPress supports the Classic Widgets screen.
<h4>Links</h4>
<ul>
<li><a href="https://github.com/5um17/classic-widgets-with-block-based-widgets" rel="nofollow ugc">GitHub repository</a></li>
</ul>

Classic Widgets with Block-based Widgets

Restore the classic widgets screen as a new menu item without replacing new block-based widgets.

Relive Classic vs Classic Widgets with Block-based Widgets