Ability to Disable Bootstrap Breadcrumbs

These aren't "Drupal Bootstrap" breadcrumbs, they're just normal breadcrumbs with only a few enhancements (to alter the items in the breadcrumb array, e.g. appending/prepending/removing certain items).

Ultimately, these items are just Render Arrays or MarkupInterface objects that are rendered into the proper Bootstrap markup.

The "enhancements" provided by this base theme can easily be disabled by overriding the plugin in a sub-theme and not calling the parent methods. Obviously if one wishes to use a module such as Easy Breadcrumb, then they need to adjust their sub-theme accordingly.

Not every module/theme is going to work "out-of-the-box" with every other single module/theme.

The responsibility lies to the developer of the site to determine which modules/themes are compatible and to fix or provide custom code (as needed) when competing functionality like this is desired.

This is called site-building.

---

Create the following file in your sub-theme and replace all instances of THEMENAME
with the lowercase machine name of your sub-theme:

./THEMENAME/src/Plugin/Preprocess/Breadcrumb.php

namespace Drupal\THEMENAME\Plugin\Preprocess;

use Drupal\bootstrap\Plugin\Preprocess\Breadcrumb as BootstrapBreadcrumb;
use Drupal\bootstrap\Utility\Variables;

/**
 * Pre-processes variables for the "breadcrumb" theme hook.
 *
 * @ingroup plugins_preprocess
 *
 * @BootstrapPreprocess("breadcrumb")
 */
class Breadcrumb extends BootstrapBreadcrumb {

  /**
   * {@inheritdoc}
   */
  public function preprocessVariables(Variables $variables) {
    // Intentionally left blank to disable base theme's alterations.
  }

}

This is a preprocess hook (as a Bootstrap base theme based OO plugin), not a template.

Even if the base theme were to search module namespaces, it would immediately be overridden by the base theme due to how the theme system works.

Theme preprocess functions are always executed after module preprocess functions.

Historically, a module could implement a theme registry alter so it could modify preprocess functions so theirs could run after. However, this has always been considered bad practice (modules shouldn't be in the theming business).

Given that this base theme's implementation is an OO based plugin (discovered by the base theme itself http://cgit.drupalcode.org/bootstrap/tree/src/Plugin/PluginManager.php#n58), only sub-themes can override the base theme's implementation.

Simply put: this cannot be implemented in a module, only a sub-theme.

It's also worth noting the following, from #2912611: how to completely disable bootstrap breadcrumb?, which implies there's actually nothing wrong with the module nor this project:

sorry, bootstrap works fine with easy breadcrumb. i had a configuration mistake.

@ Greg Boggs, I am unable to find the check boxes in the easy breadcrumbs UI from your screenshot?