A WordPress plugin that contains many blocks to build your RundizStrap theme, or you can use it with any Bootstrap 5 themes.
You can manually set CSS class(es) by referring to the Bootstrap document.
Supported custom HTML attributes like <code>data-*</code>, <code>aria-*</code> in most blocks.
Available blocks:
<ul>
<li>Customizable div</li>
<li>Layout container</li>
<li>Layout row</li>
<li>Layout column</li>
<li>Search (for navbar and anywhere else)</li>
<li>Pagination (for list posts)</li>
<li>Navbar container</li>
<li>Navbar toggler button (for responsive toggler)</li>
<li>Navbar responsive wrapper (collapse, offcanvas)</li>
<li>Navbar navigation (display menu items)</li>
<li>Button (link, or button)</li>
<li>Comment form</li>
<li>Post navigation (display next, previous post)</li>
</ul>
Tested up to PHP 8.5.
The original source code is on GitHub ( https://github.com/Rundiz-WP/rundizstrap-companion ). 
It contains the original source of blocks before compile/build and blocks that are already built, the build tools via Node package (package.json).

RundizStrap Companion

A plugin that contains blocks for the Bootstrap theme that help you customize your site in your style. All blocks are based on Bootstrap CSS.

helpful.dev

This plugin adds flexible Bootstrap 4 blocks to the WordPress editor for creating custom page layouts with the Bootstrap grid.
Are you using Advanced Bootstrap Blocks? <a href="https://wordpress.org/plugins/advanced-bootstrap-blocks/#reviews">Write a review</a>!
<h3>Blocks</h3>
Advanced Bootstrap Blocks adds the following Bootstrap 4 blocks to the WordPress editor:
<ul>
<li>Container (fixed-width or fluid, with background image settings)</li>
<li>Row</li>
<li>Column</li>
<li>Button and Button Group</li>
<li>Card with Header, Body, Footer</li>
<li>Jumbotron</li>
</ul>
<h3>Block Templates</h3>
Do you need to create standard block layouts for WordPress pages and posts? The WordPress editor lets you define custom block templates inside your theme.
The example below may get you started. Visit the <a href="https://developer.wordpress.org/block-editor/developers/block-api/block-templates/" rel="nofollow ugc">WordpPress Block Editor Handbook</a> to learn more about supercharging your WordPress themes with blocks templates.
<pre><code><?php
if(in_array('advanced-bootstrap-blocks/advanced-bootstrap-blocks.php', apply_filters('active_plugins', get_option('active_plugins')))){ 
 // do stuff only if the Advanced Bootstrap Blocks plugin is active 
 add_action( 'init', 'advancedbootstrapblocks_register_page_template' );
 function advancedbootstrapblocks_register_page_template() {
 $post_type_object = get_post_type_object( 'page' );
 $isFluid = get_theme_mod( 'understrap_container_type' ) === 'container-fluid'; 
 $post_type_object->template = [
 [ 'advanced-bootstrap-blocks/container', 
 ['className'=>'py-5', 'isWrapped' => $isFluid, 'isFluid' => false ], 
 [
 [ 'advanced-bootstrap-blocks/row', 
 [],
 [
 [ 'advanced-bootstrap-blocks/column', 
 ['className'=>'col-md-8 offset-md-2 text-center'], 
 [
 ['core/heading', 
 [ 'className' => 'display-4', 'level' => 1, 'placeholder' => 'Hello, World!', ], 
 []
 ],
 [ 'core/paragraph', 
 ['className' => 'lead', 'placeholder' => 'Lorem ipsum dolor sit amet.', ], 
 []
 ],
 ]
 ]
 ]
 ]
 ]
 ],
 ];
 }
}
</code></pre>

Advanced Bootstrap Blocks

... and that's not saying much because the others were broken or terrible. Even still, this one is on the right track, and I'm happy to see that at least somebody is getting it right. Thanks for your hard work!

So far the best bootstrap block plugin

This is really well done, it does lack some features to become perfect, and has some issues with the editor (columns chaos if multiple classes are set) but it works perfectly. By far the fastest way to get Bootstrap into Gutenberg : THUMBS UP

Very usable !

Build responsive Bootstrap 4 layouts inside the Gutenberg editor.

RundizStrap Companion vs Advanced Bootstrap Blocks