Ross Wintle

This plugin copies bookmarks from <a href="https://pinboard.in/" rel="nofollow ugc">pinboard.in</a> into a custom post type and the Pinboard tags into a custom taxonomy.
Note: This is not an official Pinboard plugin. If you have any problems please direct them to the WordPress support forums for this plugin.
This plugin:
<ul>
<li>runs automatically using either wp-cron or manually using <a href="https://wp-cli.org/" rel="nofollow ugc">wp-cli</a></li>
<li>uses the official Pinboard API (you will need your API key)</li>
<li>obeys the API’s rate limits</li>
<li>allows you to choose an author for synced pins</li>
<li>updates pins in pinboard that have been updated (I think!) but will not remove pins that have been deleted</li>
<li>provides a Gutenberg/block editor block for display a list of pins created between two specified dates</li>
</ul>
Note that this plugin does a one-way sync from Pinboard to your WordPress install. You can add your own bookmarks in WordPress but they will not be added to Pinboard.
<h4>Instructions</h4>
Once you have installed the plugin you will need to go to Settings -> Pinboard Sync and enter your API key 
(you can get this from your <a href="https://pinboard.in/settings/password" rel="nofollow ugc">Pinboard password settings screen</a>)
If you want to do automatic sync then you can then also turn on the Auto-sync option.
If you have a lot of pins in Pinboard then it is not recommended that you turn on auto-sync right away as this will probably time out or do bad things.
If you are able then the recommended method for doing a large initial import is to use the bundled wp-cli command: <code>wp-cli sync-pinboard</code>
<h4>WP-CLI command</h4>
If you can use <a href="https://wp-cli.org/" rel="nofollow ugc">WP-CLI</a> then you can make use of the <code>wp-cli sync-pinboard</code> command to 
do an import from Pinboard. This works particularly well for large first-time imports before you enable the automatic sync. But you could also use the system cron to run this command instead of WP cron.
<h4>Wish list / Roadmap</h4>
Things I have in mind for future development:
<ul>
<li>A shortcode for outputting lists of pins</li>
<li>Ability to only import a specified tag</li>
<li>(DONE) A Gutenberg block for displaying pins</li>
<li>Option in wp-cli command to allow re-import of all pins</li>
<li>Better front-end validation in admin screens and meta boxes</li>
<li>Better error logging, and logging in general, including WP-CLI-specific output</li>
<li>Better intial automated sync (over multiple cron runs)</li>
</ul>

Sync Pinboard

Works as it says it does. It was lacking a couple features I needed, but I reported them on github and Ross responded very quickly and was very helpful!

Pretty Good

Copies bookmarks from pinboard.in into a custom post type.

ScribbleLive

Reshift Media Inc.

Ghali

ScribbleLive’s all-in-one content marketing platform combines predictive analytics with content planning, creation, and distribution to deliver optimized business results. The platform’s strengths include real-time content publishing, discovery of high impact articles and opinions, influencer analysis, social curation and moderation, content-centric analytics, and unique interactive experiences from pinboards to timelines and polls.
The ScribbleLive WP Plugin unlocks added SEO benefits while maintaining the flexibility and ease-of-use of the ScribbleLive platform.
Features:
<ul>
<li>Embed ScribbleLive content with easy to use shortcode.</li>
<li>Adds SEO-friendly versions of ScribbleLive embedcodes.</li>
<li>Advanced SEO tools for better control over rel=nofollow link attributes.</li>
<li>Allows users with filtered html restrictions to embed ScribbleLive embedcodes in posts, pages and custom post types .</li>
<li>Fully cached API calls for best performance.</li>
<li>Developer filters to manage and edit cache settings.</li>
</ul>

ScribbleLive WP

The ScribbleLive WP Plugin unlocks added SEO benefits for your ScribbleLive-powered content experiences.

Sync Pinboard vs ScribbleLive WP