How to reproduce:
1. Open the attached 'URP-iOS-issue.zip' project
2. Open 'SampleScene' Scene and observe the Scene View
3. Go to File-> Build Settings-> Switch to iOS Platform
4. Build for iOS and deploy the Xcode project to the iOS device

Expected result: GameObjects look the same as in Editor
Actual result: White and black artifacts appear on objects when Normal map is assigned

Reproducible with: 2018.4.23f1(4.1.0), 2019.3.14f1(7.1.3), 2020.1.0b9(8.1.0), 2020.1.0a10(7.1.7, 8.1.0)

Reproducible with:
- iPad Air 2 (iOS 11.0.3)
- iPhone 6 (iOS 12.0) (user's info)
- iPad Air 6th gen (iOS 13.3) (user's info)
- iPad Air 2 (iOS 12.0) (user's info)

Not reproducible with:
- iPhone 8 (iOS 12.0)
- iPhone XR (iOS 13.4.1)
- VLNQA00314, Lge Nexus 5X (Nexus 5X), Android 8.0.0, CPU: Snapdragon 808, GPU: Adreno (TM) 418
- VLNQA00069, Motorola Moto G (5) Plus (Moto G (4)), Android 7.0, CPU: Snapdragon 617 MSM8952, GPU: Adreno (TM) 405
- VLNQA00052, Xiaomi MI MAX (MI MAX), Android 7.0, CPU: Snapdragon 617 MSM8952, GPU: Adreno (TM) 510
- VLNQA00320, Xiaomi - (Redmi Note 8 Pro), Android 9, CPU: MediaTek Helios G90T MT6785T, GPU: Mali-G76 MC4
- macOS Standalone

Notes:
- Screenshots of the issue are attached in Edit
- Not reproducible on Built-in pipeline
- Could reproduce on Metal and openGLES 2
- Could not reproduce the issue with Unity meshes, custom FBX models
- Could not reproduce the issue with other texture maps (Metallic, Albedo, Height)