En AppDelegate.h, haz lo siguiente:

#import "AppDelegate.h"
#import <AppsFlyerLib/AppsFlyerLib.h>
#import <AppTrackingTransparency/AppTrackingTransparency.h>
#import <UserNotifications/UserNotifications.h>
@interface AppDelegate ()
@end
@implementation AppDelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // 1 - Obtén las preferencias de AppsFlyer del archivo .plist
    NSString *path = [[NSBundle mainBundle] pathForResource:@"afdevkey_donotpush" ofType:@".plist"];
    NSDictionary* properties = [NSDictionary dictionaryWithContentsOfFile:path];
    if (properties == nil || path == nil) {
        [NSException raise:@"Error" format:@"No se puede encontrar el archivo .plist"];
    }
    NSString* appsFlyerDevKey = [properties objectForKey:@"appsFlyerDevKey"];
    NSString* appleAppID = [properties objectForKey:@"appleAppID"];
    if (appsFlyerDevKey == nil || appleAppID == nil) {
        [NSException raise:@"Error" format:@"No se puede encontrar appsFlyerDevKey o appleAppID"];
    }
    // 2 - Sustituye 'appsFlyerDevKey' y `appleAppID` por tu DevKey y tu ID de app de Apple
    [[AppsFlyerLib shared] setAppsFlyerDevKey:appsFlyerDevKey];
    [[AppsFlyerLib shared] setAppleAppID:appleAppID];
    [AppsFlyerLib shared].delegate = self;
    //  Establece isDebug en true para ver los registros de depuración de AppsFlyer
    [AppsFlyerLib shared].isDebug = true;

    if (@available(iOS 10, *)) {
        UIUserNotificationSettings *settings = [UIUserNotificationSettings settingsForTypes: UIUserNotificationTypeAlert | UIUserNotificationTypeSound | UIUserNotificationTypeBadge categories:nil];
        [[UIApplication sharedApplication] registerUserNotificationSettings:settings];
        [[UIApplication sharedApplication] registerForRemoteNotifications];
    }
    return YES;
}

- (void)applicationDidBecomeActive:(UIApplication *)application {
    [[AppsFlyerLib shared] start];
}

// Deep linking
// Abrir esquema de URI para iOS 9 y versiones posteriores
- (BOOL)application:(UIApplication *)application openURL:(NSURL *)url options:(NSDictionary *) options {
    [[AppsFlyerLib shared] handleOpenUrl:url options:options];
    return YES;
}
// Abrir esquema de URI para iOS 8 y versiones anteriores
- (BOOL)application:(UIApplication *)application openURL:(NSURL *)url sourceApplication:(NSString*)sourceApplication annotation:(id)annotation {
    [[AppsFlyerLib shared] handleOpenURL:url sourceApplication:sourceApplication withAnnotation:annotation];
    return YES;
}
// Abrir enlaces universales
- (BOOL)application:(UIApplication *)application continueUserActivity:(NSUserActivity *)userActivity restorationHandler:(void (^)(NSArray * _Nullable))restorationHandler {
    [[AppsFlyerLib shared] continueUserActivity:userActivity restorationHandler:restorationHandler];
    return YES;
}
// Informar de los datos de atribución de notificaciones push para los re-engagements
- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler {
    [[AppsFlyerLib shared] handlePushNotification:userInfo];
}
// Implementación de AppsFlyerLib
//Gestionar datos de conversión (deep link diferido)
-(void)onConversionDataSuccess:(NSDictionary*) installData {
    id status = [installData objectForKey:@"af_status"];
    if([status isEqualToString:@"Non-organic"]) {
        id sourceID = [installData objectForKey:@"media_source"];
        id campaign = [installData objectForKey:@"campaign"];
        NSLog(@"Se trata de una instalación no orgánica. Fuente de medios: %@  Campaña: %@",sourceID,campaign);
    } else if([status isEqualToString:@"Organic"]) {
        NSLog(@"Se trata de una instalación orgánica.");
    }
}
-(void)onConversionDataFail:(NSError *) error {
    NSLog(@"%@",error);
}
//Gestionar deep link directo
- (void) onAppOpenAttribution:(NSDictionary*) attributionData {
    NSLog(@"%@",attributionData);
}
- (void) onAppOpenAttributionFailure:(NSError *)error {
    NSLog(@"%@",error);
}
// soporte para delegado de escena
#pragma mark - Ciclo de vida de UISceneSession
- (UISceneConfiguration *)application:(UIApplication *)application configurationForConnectingSceneSession:(UISceneSession *)connectingSceneSession options:(UISceneConnectionOptions *)options API_AVAILABLE(ios(13)){
    // Se llama cuando se crea una nueva sesión de escena.
    // Usa este método para seleccionar una configuración para crear la nueva escena.
    return [[UISceneConfiguration alloc] initWithName:@"Default Configuration" sessionRole:connectingSceneSession.role];
}
- (void)application:(UIApplication *)application didDiscardSceneSessions:(NSSet *)sceneSessions  API_AVAILABLE(ios(13.0)){
    // Se llama cuando el usuario descarta una sesión de escena.
    // Si se ha descartado alguna sesión mientras la aplicación no estaba en funcionamiento, esto se llamará poco después de application:didFinishLaunchingWithOptions.
    // Usa este método para liberar los recursos específicos de las escenas descartadas, ya que no volverán.
}
@end

En AppDelegate.swift, agrega lo siguiente:

import UIKit
import AppTrackingTransparency
import AppsFlyerLib
import UserNotifications
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    var window:
    UIWindow?
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // 1 - Get AppsFlyer preferences from .plist file
        guard let propertiesPath = Bundle.main.path(forResource: "afdevkey_donotpush", ofType: "plist"),
            let properties = NSDictionary(contentsOfFile: propertiesPath) as? [String:String] else {
                fatalError("No se puede encontrar `afdevkey_donotpush`")
        }
        guard let appsFlyerDevKey = properties["appsFlyerDevKey"],
                   let appleAppID = properties["appleAppID"] else {
            fatalError("No se puede encontrar la clave `appsFlyerDevKey` o `appleAppID`")
        }
        // 2 - Sustituye 'appsFlyerDevKey' y `appleAppID` por tu DevKey y tu ID de app de Apple
        AppsFlyerLib.shared().appsFlyerDevKey = appsFlyerDevKey
        AppsFlyerLib.shared().appleAppID = appleAppID
        AppsFlyerLib.shared().delegate = self
        //  Establece isDebug en true para ver los registros de depuración de AppsFlyer
        AppsFlyerLib.shared().isDebug = true

        // iOS 10 o posterior
        if #available(iOS 10, *) {
            UNUserNotificationCenter.current().requestAuthorization(options: [.badge, .alert, .sound]) { _, _ in }
            application.registerForRemoteNotifications()
        }
        // soporte para iOS 9: se proporciona como referencia. This demo app supports iOS 13 and above
        else {
            UIApplication.shared.registerUserNotificationSettings(UIUserNotificationSettings(types: [.badge, .sound, .alert], categories: nil))
            UIApplication.shared.registerForRemoteNotifications()
        }
        return true
    }
    func applicationDidBecomeActive(_ application: UIApplication) {
        // Start the SDK (start the IDFA timeout set above, for iOS 14 or later)
        AppsFlyerLib.shared().start()
    }
    // Open Univerasal Links
    // For Swift version < 4.2 replace function signature with the commented out code
    // func application(_ application: UIApplication, continue userActivity: UIApplication, continue userActivity: NSUserActivity, restorationHandler: @escaping ([Any]?) -> Void) -> Bool { // this line for Swift < 4.2
    func application(_ application: NSUserActivity, restorationHandler: @escaping ([UIUserActivityRestoring]?) -> Void) -> Bool {
        AppsFlyerLib.shared().continue(userActivity, restorationHandler: nil)
        return true
    }
    // Open Deeplinks
    // Open URI-scheme for iOS 8 and below
    func application(_ application: UIApplication, open url: URL, sourceApplication: String?, annotation: Any) -> Bool {
        AppsFlyerLib.shared().handleOpen(url, sourceApplication: sourceApplication, withAnnotation: annotation)
        return true
    }
    // Open URI-scheme for iOS 9 and above
    func application(_ app: UIApplication, open url: URL, options: [UIApplication.OpenURLOptionsKey : Any] = [:]) -> Bool {
        AppsFlyerLib.shared().handleOpen(url, options: options)
        return true
    }
    // Report Push Notification attribution data for re-engagements
    func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable : Any], fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {
        AppsFlyerLib.shared().handlePushNotification(userInfo)
    }
}
extension AppDelegate: AppsFlyerLibDelegate {
    // Handle Organic/Non-organic installation
    func onConversionDataSuccess(_ data: [AnyHashable: Any]) {
        print("onConversionDataSuccess data:")
        for (key, value) in data {
            print(key, ":", value)
        }
        if let status = data["af_status"] as? String {
            if (status == "Non-organic") {
                if let sourceID = data["media_source"],
                    let campaign = data["campaign"] {
                    print("Esta es una instalación no orgánica. Media source: \(sourceID)  Campaign: \(campaign)")
                }
            } else {
                print("This is an organic install.")
            }
            if let is_first_launch = data["is_first_launch"] as?
            }
            if let is_first_launch = data["is_first_launch"] as? Bool,
                is_first_launch {
                print("Primer inicio")
            } else {
                print("No es el primer inicio")
            }
        }
    }
    func onConversionDataFail(_ error: Error) {
        print("\(error)")
    }
    // Gestiona Deep Linking
    func onAppOpenAttribution(_ attributionData: [AnyHashable: Any]) {
        // Gestiona los Datos de atribución de Deep Linking
        print("Datos de onAppOpenAttribution:")
        for (key, value) in attributionData {
            print(key, ":",value)
        }
    }
    func onAppOpenAttributionFailure(_ error: Error) {
        print("\(error)")
    }
}