Flector

The plugin allows you to manage the values of the “rel” attribute in comment links. You can enable or disable the "ugc" and "nofollow" values for all links in comments (separately for the comment author’s links and separately for links within the comment).
Help from Google:
rel="ugc": UGC stands for User Generated Content, and the ugc attribute value is recommended for links within user generated content, such as comments and forum posts.
rel="nofollow": Use this attribute for cases where you want to link to a page but don’t want to imply any type of endorsement, including passing along ranking credit to another page.
You can read more in the Google <a href="https://webmasters.googleblog.com/2019/09/evolving-nofollow-new-ways-to-identify.html" rel="nofollow ugc">blog</a>.
The plugin’s additional features include the ability to hide comment links from Yandex (by inverting them with <!––noindex––><!––/noindex––> tags).
If you liked my plugin, please rate it.

UGC Comments

cool :)

The plugin allows you to manage the values of the "rel" attribute in comment links ("ugc", "nofollow").

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.

UGC Comments vs WP UGC Comments