Per Object FX is an easy way to add FX to a single object.
Add the POFX component to the gameObject, and choose the FX from a list.
The effects are applied after the existing shader, it doesn't replace the original material.
If you hide the original mesh, the effects are applied to the background of the object. So you can create some zones where the FX is applied to all the objects inside.
FX for MeshRenderer & SkinnedMeshRenderer:
Blur, pixelate Emboss, Sobel, Refraction, Desaturate, HSL, Rim, Outline, Matcap
FX for SpriteRenderer:
Blur, pixelate Emboss, Sobel, Desaturate, HSL
New : Compatible with URP
Tested on Windows, Android, HTC vive
Source code included
