Georgi Popov

This plugin provides a list of similar / related entries to an article or a custom post type entry.
This list could be added in the form of a:
<ol>
<li>Gutenberg Block</li>
<li>Shortcode</li>
<li>Widget</li>
</ol>
If you add a widget to the sidebar it will only appear when on the details view of an entry, as similarity cannot be calculated when on a list page of multiple entries.
The syntax for the shortcode is <code>[magadanski-similar-posts id="" post_type="" taxonomy="" limit=""]</code>
You can use the attributes as follows:
<ol>
<li>ID — (integer) the ID of the post you’d like to get similar posts for. Default value: the current post ID.</li>
<li>post_type — (string) the post type you’d like to query. Default value: “post”.</li>
<li>taxonomy — (string) the taxonomy based on which you’d like to get similar items. Default value: “category”.</li>
<li>limit — (integer) a maximum number of results you’d like to receive. Default value: 5.</li>
</ol>
The similarity is considered based on the number of common categories (or other taxonomy terms) for this post and the rest of the posts in your blog.

M Similar Posts

This plugin lists similar to the current post based on the number of common categories.

ryokurosu

This plugin is a better way to set a similar post in article. 
All you have to do is setting a shortcode.This plugin works setting similar post.

Simple Shortcode Similar Post

This is a better way to view similar post.

M Similar Posts vs Simple Shortcode Similar Post