Andrei Zhitkov

Defining your default canonical arbitrary is most useful for those unfortunate souls who have their site URLs in punycode. This plugin allows setting a default custom URL to be used as canonical. It is designed to work with Yoast SEO only. The individual settings are still available and can be edited as before. Since it is dependent on presence of Yoast SEO, this plugin will not activate without it. 
The plugin does not add its own settings page, It uses WordPress Settings -> General. Look for it at the bottom of that page.
<h3>Technical Details</h3>
Supported versions: 
WordPress 4.x 
WordPress 5.x 
WordPress 6.x 
Yoast SEO 6.x-20.x

Custom canonical URL for Yoast SEO

This plugin allows setting a default custom URL to be used as canonical. It is designed to work with Yoast SEO only.

Harsh Agrawal

Content syndication is a process of amplifying your content to other blogs without hurting the SEO of your original content. You can let other blogs to republish your content in exact format with rel=canonical tag.
You can read about Rel=canonical tag here at pt.4: https://support.google.com/webmasters/answer/139066?hl=en
In this guide you can learn everything about using content syndication for content marketing: http://www.shoutmeloud.com/relcanonical-wordpresss-content-syndication-seo.html
Canonical SEO Content syndication plugin adds a meta box at post editor section. You can add permalink of post where the content was originally published. Popular blogs like bufferblog, readwriteweb are taking advantage of content syndication and rel=canonical tags.

Canonical SEO Content Syndication WordPress Plugin

Canonical SEO Content syndication plugin adds rel=canonical tag for content syndication. The meta box is added at edit post section.

Custom canonical URL for Yoast SEO vs Canonical SEO Content Syndication WordPress Plugin