Hi @BiBonino,
I would not recommend loading files directly out of your file system, especially if they references any other assets. It can cause security issues in some browser.
Instead you can use a simple static server, like the node package http-server. See https://github.com/CesiumGS/cesium/tree/main/Documentation/OfflineGuide#3d-tiles-gltf-and-other-static-files