Reproduction steps:
1. Create a new project and Import the attached custom Package "screenTearing.unitypackage"
2. In the Project window under "Assets/Scenes" open "SampleScene.unity" and switch to WebGL Platform
3. Build for WebGL
4. Use https://app.netlify.com for hosting the WebGL Build
5. Enter the address generated by https://app.netlify.com
6. Once the Quad appears rotate the device

Expected result: rendered camera view on a Quad does not start tearing when switching from Portrait to Landscape on Android WebGL
Actual result: rendered camera view on a Quad starts tearing when switching from Portrait to Landscape on Android WebGL (See attached Results.png)

Reproduces on: 2018.4.28f1, 2019.4.13f1, 2020.1.8f1, 2020.2.0b7, 2021.1.0a1

Reproduced on these devices:
VLNQA00316, Samsung Galaxy Note10 (SM-N970F), Android 9, CPU: Exynos 9 Series 9825, GPU: Mali-G76

Could not test on these devices(Due to failing to access the camera):
N/A, Samsung Galaxy S9 (SM-G960F), Android 8.0.0, CPU: Exynos 9 Series 9810, GPU: Mali-G72
N/A, Lge LG V50 ThinQ (LM-V500N), Android 10, CPU: Snapdragon 855 SM8150, GPU: Adreno (TM) 640