Tim van Iersel

Adds the rel=”ugc” attribute value to links in comments and author URLs. This way the search engines will know that the links in the are added by users (User Generated Content).
Currently the plugins adds the value ugc after the nofollow value. Not all SEO tools and search engines are up-to-date and actively supporting the new attribute values.
This plugin won’t get further updates as WordPress 5.3 has the exact same attribute values implemented (nofollow, ugc).

WP UGC Comments

Adds the "ugc" value to the rel attribute for all links in comments and the author URLs.

ugcplugin

UGC Creator is a powerful and easy-to-use WordPress plugin that empowers your users to submit posts from the frontend of your website.
UGC Creator offers a front-end form allowing visitors to submit posts and upload images with ease. Simply insert the following shortcode into any Post or Page:
<pre><code>[ugc_plugin]
</code></pre>
Our plugin is built with the highly versatile and user-friendly <a href="https://editorjs.io/" rel="nofollow ugc">Editor.js</a>, providing your users with an array of formatting and styling options to create stunning, professional-grade posts. UGC Creator supports a range of content types, including text, images, and videos, making it the perfect tool for any website that relies on user-generated content.

UGC Creator

Plugin for User-Generated Content: Get frontend post with an array of formatting and styling options to create stunning, professional-grade posts.

WP UGC Comments vs UGC Creator