glTF data cannot be loaded directly as it is not geo-referenced.

You can however use it as a 3D icon style when you visualize a point. The map then shows the glTF 3D mesh at the location specified by the point:

const painter = new FeaturePainter();
painter.paintBody = function(geoCanvas, feature, shape, layer, map, paintState) {
  const icon3DStyle = {
    meshUrl: "car.gltf"
  geoCanvas.drawIcon3D(shape, icon3DStyle);