12 files declare their use of Breadcrumb in Drupal 10

BookBreadcrumbBuilder.php in core/modules/book/src/BookBreadcrumbBuilder.php

BreadcrumbManagerTest.php in core/tests/Drupal/Tests/Core/Breadcrumb/BreadcrumbManagerTest.php

BreadcrumbTest.php in core/tests/Drupal/Tests/Core/Breadcrumb/BreadcrumbTest.php

CommentBreadcrumbBuilder.php in core/modules/comment/src/CommentBreadcrumbBuilder.php

ForumBreadcrumbBuilderBase.php in core/modules/forum/src/Breadcrumb/ForumBreadcrumbBuilderBase.php

HelpBreadcrumbBuilder.php in core/modules/help_topics/src/HelpBreadcrumbBuilder.php

LayoutBuilderBreadcrumbAlterTest.php in core/modules/layout_builder/tests/src/Kernel/LayoutBuilderBreadcrumbAlterTest.php

layout_builder.module in core/modules/layout_builder/layout_builder.module

Provides hook implementations for Layout Builder.

layout_builder_test.module in core/modules/layout_builder/tests/modules/layout_builder_test/layout_builder_test.module

Provides hook implementations for Layout Builder tests.

menu_ui.module in core/modules/menu_ui/menu_ui.module

Allows administrators to customize the site's navigation menus.

PathBasedBreadcrumbBuilder.php in core/modules/system/src/PathBasedBreadcrumbBuilder.php

TermBreadcrumbBuilder.php in core/modules/taxonomy/src/TermBreadcrumbBuilder.php