Note that /usr/usr is also a bug I have run into in the past with KiCad and created a symlink in order for this to work in the past. This is also referred to in https://forum.kicad.info/t/3d-models-not-showing/12494/9. Also see https://forum.kicad.info/t/3d-viewer-not-showing-3d-models-after-update-to-nightly/6153/17