I made this tool so I could quickly try out skyboxes from HDRIHaven in Unity with one click.
It shows a browser with previews that can be clicked to download, create skybox materials and assign it to lighting settings.
To access the browser, you need to create an importer. Right-click in project view -> Create -> Steal With Attribution -> HDRI Importer project
Using openupm:
openupm add com.johanhelsing.stealwithattribution