11 files declare their use of LinkItemInterface in Zircon Profile 8

EntityContentBase.php in core/modules/migrate/src/Plugin/migrate/destination/EntityContentBase.php

Contains \Drupal\migrate\Plugin\migrate\destination\EntityContentBase.

LinkFieldTest.php in core/modules/link/src/Tests/LinkFieldTest.php

Contains \Drupal\link\Tests\LinkFieldTest.

LinkFieldUITest.php in core/modules/link/src/Tests/LinkFieldUITest.php

Contains \Drupal\link\Tests\LinkFieldUITest.

LinkFormatter.php in core/modules/link/src/Plugin/Field/FieldFormatter/LinkFormatter.php

Contains \Drupal\link\Plugin\Field\FieldFormatter\LinkFormatter.

LinkItem.php in core/modules/link/src/Plugin/Field/FieldType/LinkItem.php

Contains \Drupal\link\Plugin\Field\FieldType\LinkItem.

LinkItemTest.php in core/modules/link/src/Tests/LinkItemTest.php

Contains \Drupal\link\Tests\LinkItemTest.

LinkTypeConstraint.php in core/modules/link/src/Plugin/Validation/Constraint/LinkTypeConstraint.php

Contains \Drupal\link\Plugin\Validation\Constraint\LinkTypeConstraint.

LinkWidget.php in core/modules/link/src/Plugin/Field/FieldWidget/LinkWidget.php

Contains \Drupal\link\Plugin\Field\FieldWidget\LinkWidget.

MenuLinkContent.php in core/modules/menu_link_content/src/Entity/MenuLinkContent.php

Contains \Drupal\menu_link_content\Entity\MenuLinkContent.

MigrateFieldInstanceTest.php in core/modules/field/src/Tests/Migrate/d6/MigrateFieldInstanceTest.php

Contains \Drupal\field\Tests\Migrate\d6\MigrateFieldInstanceTest.

Shortcut.php in core/modules/shortcut/src/Entity/Shortcut.php

Contains \Drupal\shortcut\Entity\Shortcut.