XL87LGV7W9EY7Y7A5Z9B3T7N6ZRX74 I also tried using the graphene location toggle, but that did not work; I believe it briefly gave a different error, perhaps "service not available" when attempting a geolocation on the map. The map definitely looks like a Google Maps implementation, so I continue to wonder if graphene is not compatible with one of the Google geocoding APIs (Maps Javascript API client geocoder perhaps?)
See here for more:
https://developers.google.com/maps/documentation/geocoding/overview
A couple of observations about the Merlin app; I tested it in a factory reset Android 11 today to see its stock behavior. The geolocation lookup interface is really not great even in stock Android; for example, despite having all permissions and scanning enabled, it does not seem to use anything but GPS to get a location; if you are indoors it will simply spin. So when I tested graphene again I made sure to have a GPS lock, but no luck.