Существует обратный вызов onDestroy
от componentRef, который вы можете подключить для очистки подписок
/**
* A lifecycle hook that provides additional developer-defined cleanup
* functionality for the component.
* @param callback A handler function that cleans up developer-defined data
* associated with this component. Called when the `destroy()` method is invoked.
*/
abstract onDestroy(callback: Function): void;
Пример
const sub=this.componentRef.instance.output.subscribe(event => console.log(event));
this.componentRef.onDestroy(()=>{
sub.unsubscribe()
})