Reproduction steps:
1. Open the attached project.
2. Make sure Graphics API is set to OpenGLES2.
3. Build and run it on an iOS device.

Actual result:
- Stencil buffer doesn't work. Text appears outside of Scroll View (Screenshot attached).

Expected result:
- Text appears within Scroll View (Screenshot attached).

Reproduced with:
- iOS (GLES2)
- 2019.2.1f1, 2020.1.0a3
- iPhone 7+ iOS 12.0, iPhone X iOS 11.3.1, iPhone 5 iOS 10.3.3

Not reproducible with:
- iOS (GLES3, Metal)
- Android (GLES2, GLES3)
VLNQA00128 Samsung Galaxy Note8 9 Exynos 9 Octa 8895 Mali-G71 OpenGL ES 3.2
VLNQA00282 Samsung Galaxy S10e 9 Snapdragon 855 SM8150 Adreno (TM) 640 OpenGL ES 3.2

Note:
- The project doesn't open with older Unity versions.