11 files declare their use of DomainNegotiatorInterface in Domain Access 8

CurrentDomainContext.php in domain/src/ContextProvider/CurrentDomainContext.php

Domain.php in domain/src/Entity/Domain.php

Domain.php in domain/src/Plugin/views/access/Domain.php

DomainAccessCheck.php in domain/src/Access/DomainAccessCheck.php

DomainAccessManager.php in domain_access/src/DomainAccessManager.php

DomainConfigLibraryDiscoveryCollector.php in domain_config/src/DomainConfigLibraryDiscoveryCollector.php

DomainInterface.php in domain/src/DomainInterface.php

DomainRouteCheck.php in domain/src/Access/DomainRouteCheck.php

DomainSourcePathProcessor.php in domain_source/src/HttpKernel/DomainSourcePathProcessor.php

DomainSubscriber.php in domain/src/EventSubscriber/DomainSubscriber.php

domain_alias.module in domain_alias/domain_alias.module

Maps multiple host requests to a single domain record.