After getting more into Shaders, I was able to solve it:
Fog of War Shader is for WebGL2 only.
Also I wanted to share my old Shader (only WebGL1) for i.e. RTS/RPG Entity Selection Circles:
After getting more into Shaders, I was able to solve it:
Fog of War Shader is for WebGL2 only.
Also I wanted to share my old Shader (only WebGL1) for i.e. RTS/RPG Entity Selection Circles: