try
Open a cached layer/coverage for a CacheEntry that has no registered web service — i.e. the content was imported directly into the cache (e.g. a standalone .gpkg file with no gpkg_web_service row). Returns null when the backend can't construct a layer in this mode.
GeoPackage-backed managers override this to provide their gpkg-native opener (per-data-type layer reconstruction from gpkg_contents rows). Other backends keep the default no-op.