ElevationProfileLineQuery

const elevLayer = new ElevationLayer({
  url: "https://sampleserver6.arcgisonline.com/arcgis/rest/.../Elevation/ImageServer"
});

// profile line with elevation layer source
const elevationProfile = new ElevationProfile({
  view,
  profiles: [{
    type: "query", // autocasts as new ElevationProfileLineQuery(),
    source: elevLayer
  }]
});

// profile line with a source coming from an elevation
// layer with a specific sampling resolution
const elevationProfile = new ElevationProfile({
  view,
  profiles: [{
    type: "query",
    source: {
      queryElevation(geometry, options) {
        return elevLayer.queryElevation(geometry, { ...options, demResolution: 20 })
      }
    }
  }]
});

// profile line with a source that queries data
// on an elevation sampler
view.when(async() => {
  const sampler = await elevLayer.createElevationSampler(extent);
  const querySource = {
    queryElevation: async (geometry: Multipoint) => {
      return {
        geometry: await sampler.queryElevation(geometry),
        noDataValue: sampler.noDataValue
      };
    }
  };
  const elevationProfile = new ElevationProfile({
    view,
    profiles: [{
      type: "query",
      source: querySource
    }]
  });
});