Reproduction steps:
1. Open the attached user's project "UIToolkit.zip"
2. Build for Android
3. Observe the video being translucent

Expected result: VP8 WebM video with transparency does not render as translucent in UI Toolkit
Actual result: VP8 WebM video with transparency rendering as translucent in UI Toolkit

Reproduces on: 2021.2.15f1
Does not reproduce on: 2022.2.0a8, 2022.1.0b11
Could not test on 2019.4.36f1 and 2020.3.32f1 due to the scripting errors when downgrading the project

Reproducible on these devices:
VLNQA00381, Xiaomi Redmi Note 8 Pro (Redmi Note 8 Pro), Android 9, CPU: MediaTek Helios G90T M6785T, GPU: Mali-G76 MC4
VLNQA00404 - Galaxy Z Flip3 5G (SM-F711B), OS: 11, CPU: Snapdragon 888, GPU: Adreno 660
VLNQA00410 - Galaxy Z Fold3 5G (SM-F926U), OS: 11, CPU: Snapdragon 888, GPU: Adreno 660
VLNQA00263 - Google Pixel 3 (Pixel 3), OS: 12.0.0, CPU: Snapdragon 845, GPU: Adreno 630
N/A, Samsung - (SM-G991U), Android 11, CPU: Snapdragon 888, GPU: Adreno (TM) 660
N/A, Google Pixel 3 (Pixel 3), Android 12, CPU: Snapdragon 845, GPU: Adreno (TM) 630

Not reproducible on these devices:
VLNQA00052, Xiaomi MI MAX (MI MAX), Android 7.0, CPU: Snapdragon 617 MSM8952, GPU: Adreno (TM) 510
VLNQA00380, Xiaomi MI 8 Lite (MI 8 Lite), Android 9, CPU: Snapdragon 660, GPU: Adreno (TM) 512
N/A, Huawei - (ELS-NX9), Android 10, CPU: NOT FOUND, GPU: Mali-G76
VLNQA00264, Samsung Galaxy S10+ (SM-G975F), Android 10, CPU: NOT FOUND, GPU: Mali-G76
VLNQA00006 - Samsung Galaxy S7 (SM-G930F), OS: 8.0.0, CPU: Exynos 8 Octa (8890), GPU: Mali-T880
VLNQA00277 - Asus ROG Phone (ASUS_Z01QD), OS: 9.0.0, CPU: Snapdragon 845 SDM845, GPU: Adreno 630
VLNQA00219 - Samsung Galaxy Note9 USA (SM-N960U), OS: 8.1.0, CPU: Snapdragon 845 SDM845, GPU: Adreno 630
VLNQA00147 - Razer Phone (Cheryl), OS: 8.1.0, CPU: Snapdragon 835 MSM8998, GPU: Adreno 540
VLNQA00121 - Samsung Galaxy S9 (SM-G960F), OS: 9.0.0, CPU: Exynos 9 Series 9810, GPU: Mali-G72
N/A, Xiaomi Mi Note2 (Mi Note 2), Android 8.0.0, CPU: Snapdragon 820 MSM8996, GPU: Adreno (TM) 530
N/A, Vivo V1924A (V1924A), Android 10, CPU: Snapdragon 855 SM8150, GPU: Adreno (TM) 640
N/A, Samsung Galaxy Note10+ (SM-N975F), Android 9, CPU: Exynos 9 Series 9825, GPU: Mali-G76
VLNQA00391, Xiaomi Redmi 9A (M2006C3LG), Android 10, CPU: MediaTek Helio G25 (MT6762G), GPU: PowerVR Rogue GE8320
N/A, Oppo Reno Z 中国版 (PCDM10), Android 11, CPU: NOT FOUND, GPU: PowerVR Rogue GM9446
VLNQA00335, Samsung Galaxy S20+ 5G (SM-G986B), Android 10, CPU: Exynos 990, GPU: Mali-G77

Could not test with:
VLNQA00176, Xiaomi Redmi 4 (Redmi 4), Android 6.0.1, CPU: Snapdragon 430 MSM8937, GPU: Adreno (TM) 505 (video is not rendered, black screen)
VLNQA00022 - Xiaomi Redmi Note 3 (Redmi Note 3), OS: 6.0.1, CPU: Snapdragon 650 MSM8956, GPU: Adreno 510 (video is not rendered, black scene)
iPhone 13 mini (iOS 15)
iPad 6th generation (iOS 14.4.2)

Notes:
-In the attached user's project, the video code is on line ~220 of "Assets/UIToolkitDemo/AppScript.cs" and the video is stored in "Assets/UIToolkitDemo/Resources/"
-Issue does not reproduce in the Editor