However, if you have an RTX 2060 or better, you should use the paid or the new ReShade 6.0 Path Tracing beta, because they include temporal denoising (less flicker).
Here’s the complete relevant content and where to find it: reshade ray tracing shader rtgi 033 free
"RTGI is greyed out / says 'Failed to compile.'" Solution: You are missing the ReShade.fxh file or using an outdated ReShade version. Download ReShade 5.0 or newer. However, if you have an RTX 2060 or