How to reproduce:
1. Open the attached “repro-project”
2. File → Build Settings and change Platform to WebGL and check Development Build
3. Click Build
4. Run the WebGL build on a local server (python http.server was used in testing)
5. Connect to the server through a mobile device browser and observe

Expected result: The rendered spotlight has a checkmark shape.
Actual result: The rendered spotlight is round.

Reproducible with: 2021.3.17f1, 2022.2.3f1, 2023.1.0b1 (Does not render spotlight at all)
Could not test with: 2020.3.44f1 (No Light settings required to add a cookie)

Reproducible on: macOS 13.2 (Intel)

Reproducible on devices:
VLNQA00277, Asus ROG Phone (ASUS_Z01QD), Android 9, CPU: NOT FOUND, GPU: Adreno (TM) 630
VLNQA00334, Xiaomi Mi A3 (Mi A3), Android 11, CPU: Snapdragon 665 SM6125, GPU: Adreno (TM) 610

Not reproducible on these devices:
VLNQA00134, Samsung Galaxy S8 (SM-G950F), Android 9, CPU: Exynos 9 Octa 8895, GPU: Mali-G71
VLNQA00331, Huawei P20 lite (ANE-LX1), Android 9, CPU: HiSilicon Kirin 659, GPU: Mali-T830
iPhone 12 Pro Max, iOS 16.1, Safari

Notes: Regular Google browser was used in all Android reproductions. No reproduction on macOS using Brave browser (Chromium).