10 files declare their use of MenuInterface

LinksetController.php in core/modules/system/src/Controller/LinksetController.php
Menu.php in core/modules/system/src/Entity/Menu.php
MenuBlockTest.php in core/modules/menu_ui/tests/src/Kernel/MenuBlockTest.php
MenuController.php in core/modules/menu_link_content/src/Controller/MenuController.php
MenuController.php in core/modules/menu_ui/src/Controller/MenuController.php
MenuLinkContentForm.php in core/modules/menu_link_content/src/Form/MenuLinkContentForm.php
menu_link_content.module in core/modules/menu_link_content/menu_link_content.module
Allows administrators to create custom menu links.
menu_ui.module in core/modules/menu_ui/menu_ui.module
Allows administrators to customize the site's navigation menus.
PluginExistsConstraintValidatorTest.php in core/tests/Drupal/KernelTests/Core/Plugin/PluginExistsConstraintValidatorTest.php
SystemMenuOffCanvasForm.php in core/modules/system/src/Form/SystemMenuOffCanvasForm.php

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