Add info about affected app services

source/deprecation.txt

@@ -25,6 +25,51 @@ move to an alternative solution or remove Sync before September 30, 2025. Refer
 to the :ref:`App Services deprecation page <app-services-deprecation>` for more
 information.
 
+Additional Impacted App Services Capabilities
+---------------------------------------------
+
+Some App Services are affected by the deprecation of the Device SDKs. These
+services will no longer function as expected when the SDKs reach end-of-life and
+are not supported.
+
+Authentication and User Management
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The Device SDKs are the primary entry point for :ref:`App Services
+Authentication and User Management <users-and-authentication>`, an
+authentication service for your applications. As part of the SDK deprecation,
+this feature will no longer be available when the SDKs reach end-of-life and are
+removed. You must move to an alternative authentication service before that time
+to avoid disruption in your application.
+
+The feature supports multiple :ref:`authentication providers 
+<authentication-providers>`, and your migration to alternative solutions depends
+on your provider. To identify the best alternative for your use case, please
+contact your Account team.
+
+Given App Services Authentication is no longer available, Authentication
+Triggers will no longer be executed when user events (for example: login or
+create) occur. This authentication logic will need to be implemented along with 
+the chosen alternative solution.
+
+Functions
+~~~~~~~~~
+
+Functions will continue to be available within the context of Triggers. Use
+cases where a function was being directly accessed through a Realm SDK are
+impacted and must migrate to a different solution. 
+
+Wire Protocol
+~~~~~~~~~~~~~
+
+App Services Wire Protocol is also deprecated alongside the Realm SDKs.
+
+Data Access Permissions
+~~~~~~~~~~~~~~~~~~~~~~~
+
+Data Access Permissions (Rules and Roles) are also deprecated alongside Device
+Sync.
+
 Device SDKs Community Branches
 ------------------------------