How do I display the content of React Quill without the html markup?

You need html-react-parser

import Parser from 'html-react-parser';

...     // in your render
<ReactQuill
    ...
    value={code} 
    onChange={this.previewCode}
/>
...
{Parser(code)}

After doing some research I was able to find the answer:

To display the content of Quill in the preview section without the html tags I used this code:

      <div dangerouslySetInnerHTML={{__html: this.state.content}}></div>

The simplest way is to use the same react-quill component with editing disabled. This method doesn't need you to install any extra package. You can do it by passing a prop readOnly whose value is set to true (By default it is false)

Here is the code for the component which you can use to preview side:

<ReactQuill
   value={this.state.content}
   readOnly={true}
   theme={"bubble"}
/>

This is how it will look like:

Note: ReactQuill comes with two inbuilt themes (bubble and snow).

Here is how it looks in the snow theme. It has a toolbar at the top:

And here is how it looks in bubble theme.

You should use the "bubble" theme by passing the string "bubble" in the theme prop to display your editor content. This is because it does not have a toolbar at the top like the "snow" theme.

In order to use the bubble theme, you'll also have to import a CSS stylesheet for this specific theme as follow:*

import 'react-quill/dist/quill.bubble.css'

onChange(content, delta, source, editor) {
  const text = editor.getText(content);
  this.setState ({ content: text });
  console.log(text)
}