So yes it does work on playground - but the very same textures don’t work on my Visual Studio Code → Live Server or on my local python3 HTTP server.
I wonder if you have any examples for how to resolve this - Playground is good for trying out snippets but developing a more full-fledged app on it doesn’t seem very efficient to me… Thus the need to resolve skyboxes, such an important part of any 3D environment.
you should try simply with npx http-server a tiny node based server to see what you have. At least you could validate that you are simply not setting the path incorrectly for instance.