Greenscreen Within Eevee Pro brings chroma-keying into Blender's material nodes, so greenscreen footage can sit inside a 3D scene without exporting a PNG sequence beforehand. It handles greenscreen, bluescreen, redscreen and other colours, and runs in both Eevee and Cycles.
Because the keyed footage lives in the scene, live-action actors can cast shadows, receive shadows and appear in reflections, and they react to scene lighting. The addon is designed for cheap greenscreens and works on any screen colour.
One practical use is filming actors on a still camera and then creating smooth CGI camera moves in 3D. Documentation is included, and a demo video is available. It's released under the GPL license and supports a wide range of Blender versions, from 2.8 through 3.4.