Gradient Skies is a Blender add-on from Egret Studios LLC for creating sky backgrounds directly inside your scene. Rather than building the effect by hand, it produces skies without manual node wiring, so the setup stays inside Blender.
The add-on works with both the Cycles and Eevee render engines and supports a range of Blender versions from 4.0 through 5.1. It's marked as compatible with the Blender extensions system, so it can be installed through Blender's extension workflow. Documentation is included to guide you through using it inside Blender.
Gradient Skies is distributed under the GPL license. A demo video is available for a closer look, and this catalog lists the add-on as free — check the developer's page for current licensing and pricing details.