As a custom build, it is installed as a separate version of Blender rather than a simple add-on. K-Cycles - Superhive (formerly Blender Market)

Developed by Eric Klein, K-Cycles focuses on maximizing hardware utilization, primarily for using OptiX and CUDA, though it also supports HIP for AMD.

Includes global illumination and sampling presets that allow users to quickly toggle between "fast" preview settings and "high-quality" final render modes. Exclusive Toolset

It is fully compatible with standard Cycles settings and all existing Blender add-ons, allowing users to switch between standard Blender and K-Cycles without losing scene data.