Garmin Connect Web has a map display option for OpenStreetMap. When I check the map, it's hosted in servers like connectosm16.azureedge.net. So it's a space for Connect on Azure. So Garmin has a control on them. However, these maps are really really old, maybe three years old. I know because I mapped almost all forest roads in my area but almost none are present in OSM option in Connect web.
So please update these maps, it shouldn't be very hard process.