Igor Benic

This is a plugin that will enable you to add alerts, info and similar chunks of text.
This is useful when creating tutorials and you want the reader to be notified of a change in code or something to check. Info blocks are used in technical Books when you want to point some information or you want the reader to read a part that is important to understand the next piece of code.
This is also suitable when you republish articles on your blog to inform the user on what has changed.
Info Blocks also allow you to change:
<ul>
<li>Background color</li>
<li>Text color</li>
<li>Padding (size and unit)</li>
<li>Dashicon Icon (or leave it off)</li>
<li>Icon Size</li>
<li>Space between the Icon and Text</li>
</ul>

Info Blocks

A gutenberg block for creating alerts, information or update text

Phil Niehus

The Maintenance Countdown plugin adds a maintenance countdown page to your wordpress installation. This gives you the 
opportunity to tell your users what you are doing and how long they need to wait until your site is back online. 
Users with the ‘edit_themes’ capability are still able to access the site when maintenance is enabled.
Features:
<ul>
<li>Enable/disable maintenance mode</li>
<li>Page title, headline, maintenance information and check back message are customizable through the dashboard</li>
<li>The end date and time for the countdown can be set through the settings page on the dashboard</li>
<li>The countdown starts counting upwards if the end time is exceeded</li>
<li>Includes 2 different designs</li>
<li>Has an option to use custom css, for more information take a look at the faq</li>
</ul>

Maintenance Countdown

This plugin adds a maintenance countdown page to wordpress.

Info Blocks vs Maintenance Countdown