private static IPersistentCache<byte[]>? _defaultCache;
private static BruTile.Attribution _stadiaAttribution = new("© Stadia Maps", "https://stadiamaps.com/");
private void CreateMapFirstTime()
{
    if (Mymap == null) return;

    Mymap.Layers.Clear();

    //OSM map <- this works, so disregard next line
    Mymap.Layers.Add(Mapsui.Tiling.OpenStreetMap.CreateTileLayer());

    #region Attempt to add Stadia map tiles -> failed
    // Stadia maps tiles
    string userAgent = 
        $"user-agent-of-{Path.GetFileNameWithoutExtension(
            System.AppDomain.CurrentDomain.FriendlyName)}";

    var httpTileSource = new HttpTileSource(
        new GlobalSphericalMercator(),
        "https://tiles.stadiamaps.com/tiles/alidade_smooth_dark/{z}/{x}/{y}@2x.png", //or {r} instead of '@2x', I've also tried plain '/{z}/{x}/{y}.png',
        ["a", "b", "c"] <- I've tried with and without, same result
        name: "Stadia Maps",
        attribution: _stadiaAttribution,
        apiKey: "xxx", //<- Unsure if this is necessary. The retina URL works in python without an api key, but I've created an api key to be sure.
        //configureHttpRequestMessage: (r) => r.Headers.TryAddWithoutValidation("User-Agent", userAgent), <- this is from Mapsui source code, but in my version of BruTile the HttpTileSource does not have this argument in the constructor. My version (5.0.6) is just the one I get when installing current Mapsui release.
        persistentCache: _defaultCache
        );

    httpTileSource.AddHeader("User-Agent", userAgent); <- instead of the one in the constructor

    var stadiaLayer = new TileLayer(httpTileSource) { Name = "Stadia" };

    // Add the custom tile layer to the map
    Mymap.Layers.Add(stadiaLayer); 
    #endregion

var tileSource = new HttpTileSource( 
    new GlobalSphericalMercator(0, 18),
    "https://tiles.stadiamaps.com/tiles/alidade_smooth_dark/{z}/{x}/{y}.png",
    ["a", "b", "c"],
    apiKey: "xxx",
    name: "Stadia");

var extent = new Extent(-20037508, -20037508, 20037508, 20037508);
var screenWidthInPixels = 400; // The width of the map on screen in pixels
var resolution = extent.Width / screenWidthInPixels;
var tileInfos = tileSource.Schema.GetTileInfos(extent, resolution);

Console.WriteLine("Show tile info");
foreach (var tileInfo in tileInfos)
{
    var tile = await tileSource.GetTileAsync(tileInfo);

    Console.WriteLine(
        $"tile col: {tileInfo.Index.Col}, " +
        $"tile row: {tileInfo.Index.Row}, " +
        $"tile level: {tileInfo.Index.Level} , " +
        $"tile size {tile.Length}");
}