If you're going to use SSGI for a commercial project, be aware that the addon is currently a shader hack, not exactly the same screen space GI you get with some game engines. This means that it does not work properly with HDRI environment lighting (yet). As mentioned on the download page, the specular component between >object reflections will give inverted colors when used with HDRI. There are als other limitations, but that's the big one. Do not use it with HDRI environments.

In general, commercial products should ,of course, only be made for use with the default "vanilla" releases of Blender with NO dependencies on third party add-ons.

"SSGI for EEVEE" mass replaces all princlpled BSFD Shaders with a special "SSGI principled Shader (see pic).

It also has a N panel where you can increase/attenuate or even completely remove the effect as well as bake the SSGI lighting to a cache file.

As already noted, the major problems are with highly relfective surfaces but also any image based textures with with SSS Shader applied while using HDRI.

The good news is that you can resolve the issues and still use HDRI lighting by simply replacing the auto created "SSGI Pricipled" shader with a standard principled BSDF on the problem material types for personal projects and still get the other bounce lighting benefits of the add-on.

or alternatively light your scenes with standard point/area/sunlamps in your EEVEE based workflow.

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