uber.onCourierEnRouteToDropoff takes no filters. It starts when the courier heads to the dropoff: status dropoff while courierImminent is false.
automations/courier-en-route-to-dropoff.automation.ts
id, deliveryId, customerId, status, liveMode, created, and the full delivery with its courier, waypoints, ETAs, and fee.
Requires an Uber Direct connection with a webhook signing key and a dashboard webhook that sends event.delivery_status. See Connect Uber Direct.