12 files declare their use of SubscriberInterface in Simplenews 8

ConfirmMultiForm.php in src/Form/ConfirmMultiForm.php

MailEntity.php in src/Mail/MailEntity.php

Mailer.php in src/Mail/Mailer.php

MailerInterface.php in src/Mail/MailerInterface.php

RecipientHandlerBase.php in src/Plugin/simplenews/RecipientHandler/RecipientHandlerBase.php

simplenews.module in ./simplenews.module

Simplenews node handling, sent email, newsletter block and general hooks

SimplenewsAdministrationTest.php in src/Tests/SimplenewsAdministrationTest.php

Subscriber.php in src/Entity/Subscriber.php

SubscriberExportForm.php in src/Form/SubscriberExportForm.php

SubscriptionManager.php in src/Subscription/SubscriptionManager.php

SubscriptionManagerInterface.php in src/Subscription/SubscriptionManagerInterface.php

SubscriptionStorage.php in src/Subscription/SubscriptionStorage.php