theMikeD

An excerpt is a (usually) brief, text-only post summary. It is used in various places of a theme when a summary of a post is needed, such as on your blog page and archive pages for terms.
Excerpts are either manually crafted or (usually poorly) automatically extracted from the main post content. Hand crafted ones are better because
<ul>
<li>they avoid things like sentences being cut off in the mid…</li>
<li>they allow you create an actual summary and not just the first x words from the post content</li>
<li>they allow you to do better SEO targeting</li>
<li>they look better</li>
</ul>
This plugin will enforce the use of hand-crafted excerpts by your users by preventing a post without an excerpt from being published.
Classic editor support is based on the work done by Scott Walkinshaw and other contributors, found <a href="https://gist.github.com/swalkinshaw/2695510" rel="nofollow ugc">here</a>.
<h3>Upgrading from a previous version</h3>
Use the upgrade link in the Dashboard (Dashboard > Updates) to upgrade this plugin.
<h3>License and Disclaimer</h3>
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License 2 as published by 
the Free Software Foundation.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
The license for this software can be found here: <a href="http://www.gnu.org/licenses/gpl-2.0.html" rel="nofollow ugc">http://www.gnu.org/licenses/gpl-2.0.html</a>

Mandatory Excerpts for WordPress

Causes the excerpt to be required before a post can be published. Supports both editor types (classic and block aka gutenberg).

Tim Eckel

Try it out on a free dummy site here => <a href="https://demo.tastewp.com/read-more-excerpt-link" rel="nofollow ugc">https://demo.tastewp.com/read-more-excerpt-link</a>
When WordPress makes an excerpt from your post content, it crops the content and adds an ellipsis […] to the end. This plugin changes the ellipsis to a Read More link to the full post content.
You can change the Read More link text to anything you wish from the Read More Excerpt submenu on the WordPress Settings menu.
Also from the Read More Excerpt submenu, you can specify the excerpt word length (WordPress defaults to 55 words).
Additionally, you can force the Read More link to show even when an excerpt is entered or when a read more tag is added to the content. This is turned on from the Read More Excerpt submenu with the Show More Frequently checkbox.
The Read More link uses the class read-more-link, so you can stylize the link any way you wish.

Mandatory Excerpts for WordPress vs Read More Excerpt Link