Steps to reproduce:
1. Create new Unity project
2. Install In-App Purchasing package (Services > In-App Purchasing > Install)
3. Open Package Manager and navigate to In-App Purchasing > Samples
4. Import “01 Buying Consumables” Sample
5. Open “01 Buying Consumables” Scene (Assets/Samples/In-App Purchasing/5.2.1/01 Buying Consumables/BuyingConsumables.unity)
6. Enter Play Mode
7. Observe the Console window

Actual results: “InvalidOperationException: You are trying to read Input using the UnityEngine.Input class, but you have switched active Input handling to Input System package in Player Settings.” errors are thrown in the Console window, Sample uses old Input System
Expected results: No errors are thrown in the Console window, Sample uses new Input system

Reproducible with versions: 6000.0.73f1, 6000.3.13f1, 6000.4.3f1, 6000.5.0b4, 6000.6.0a3

Tested on (OS): macOS Silicon Tahoe 26.4

Notes:

•  Reproducible with all available Sample scenes for In-App Purchasing package

{code:java}
InvalidOperationException: You are trying to read Input using the UnityEngine.Input class, but you have switched active Input handling to Input System package in Player Settings.
UnityEngine.Internal.InputUnsafeUtility.GetButtonDown (System.String buttonName) (at <12d97c2283844f2583a5a661ebdcbe68>:0)
UnityEngine.Input.GetButtonDown (System.String buttonName) (at /Users/bokken/build/output/unity/unity/Modules/InputLegacy/Input.bindings.cs:371)
UnityEngine.EventSystems.BaseInput.GetButtonDown (System.String buttonName) (at ./Library/PackageCache/com.unity.ugui@e153d0c6c9e8/Runtime/UGUI/EventSystem/InputModules/BaseInput.cs:154)
UnityEngine.EventSystems.StandaloneInputModule.ShouldActivateModule () (at ./Library/PackageCache/com.unity.ugui@e153d0c6c9e8/Runtime/UGUI/EventSystem/InputModules/StandaloneInputModule.cs:253)
UnityEngine.EventSystems.EventSystem.Update () (at ./Library/PackageCache/com.unity.ugui@e153d0c6c9e8/Runtime/UGUI/EventSystem/EventSystem.cs:489)
UnityEngine.StackTraceUtility:ExtractStringFromExceptionInternal(Object, String&, String&) (at /Users/bokken/build/output/unity/unity/Runtime/Export/Scripting/StackTrace.cs:50)
{code}