flutter_map: TileLayer with WMTS not showing transparent background

Question

I'm trying to add layer to my map, using package flutter_map. When using WMS, it works fine using WMSTileLayerOptions. But for WMTS, i use directly urlTemplate but can't add transparent background, there's always white background.

Did i miss something ? Is it about the url ?

    class Map extends StatelessWidget {
      const Map({super.key});
    
      @override
      Widget build(BuildContext context) {
        return FlutterMap(
          options: MapOptions(
            backgroundColor: Colors.transparent,
            initialZoom: 7,
          ),
          children: [
            TileLayer(
              urlTemplate: 'https://tile.openstreetmap.org/{z}/{x}/{y}.png',
            ),
            TileLayer(
              urlTemplate:
                  "https://wxs.ign.fr/pratique/geoportail/wmts?REQUEST=GetTile&SERVICE=WMTS&VERSION=1.0.0&TILEMATRIXSET=PM&LAYER=GEOGRAPHICALGRIDSYSTEMS.PLANIGNV2&STYLE=normal&FORMAT=image/png&TILECOL={x}&TILEROW={y}&TILEMATRIX={z}",
            ),
          ],
        );
      }
    }