6 files declare their use of UrlMatcherInterface in Zircon Profile 8

DynamicRouter.php in vendor/symfony-cmf/routing/DynamicRouter.php

LanguageNegotiationUserAdmin.php in core/modules/user/src/Plugin/LanguageNegotiation/LanguageNegotiationUserAdmin.php

Contains \Drupal\user\Plugin\LanguageNegotiation\LanguageNegotiationUserAdmin.

PathValidator.php in core/lib/Drupal/Core/Path/PathValidator.php

Contains \Drupal\Core\Path\PathValidator.

Router.php in vendor/symfony/routing/Router.php

RouterInterface.php in vendor/symfony/routing/RouterInterface.php

RouterListener.php in vendor/symfony/http-kernel/EventListener/RouterListener.php