@qglaude You underestimate SNAP
If you have opened and displayed a geocoded (WGS84) raster you can select âadd layerâ in the mapping tools:
Add a service URL of a WMS, for example the OWS terrestris OpenStreetMap
http://ows.terrestris.de/osm-gray/service?
Select a layer in the following dialogue:
Click âNextâ and âFinishâ - there you have it: