I mapped out a 60km ride on the Ride with GPS site.
The Garmin Edge 530 was right on the money at the end.
Similar "on the money" results for today's ride:
Ebike-connect (via display internal GPS) 36.5km
Ebike trip distance (internal bike odometer?) 36.5 km
Remote Tracking (via phone GPS) 36.51km
Osmand (OpenStreetMap) route planning 36.6km (about 0.3% higher)
The trip was 50:50 urban and rural riding.