This is a paid asset, but now you can download Fast Vignette (Mobile , LWRP , URP) Free.
Detail this asset from Unity Store: Original Link
Fast Vignette Mobile LWRP URP v1.0
“If possible, please buy the package to support the developer”
Works with Unity versions higher than 2017.1.0f
LWRP works only with Unity versions higher than 2019.1.0f1
URP works only with Unity versions higher than 2019.3.0f3
Fastest Solution on the market.
This package consists of the shader for applying the Vignette effect to the screen. This solution is currently the fastest in the market. The shader was tested on the low-end mobile device in the loaded scene in order to optimize the performance and fps.
* Vignette – The fastest vignette effect in the Asset Store, completely optimized. Runs at 55-58 FPS on a low-end mobile device(with proper settings).
NOTE!!! All the testing was made on low-end mobile device Meizu M2 Note in the scene containing:
-65 different gameObjects,
-68 different Materials,
-57 different Textures,
-1 Directional Light(realtime),