How to custom draw the icon for .accessoryInline lock screen widget?

Hello, I am trying to custom draw the .accessoryInline lock screen widget. When I return a Label() from a widget View, like this Label("Snow", systemImage: "snow"), the icon draws just fine, but once I try to draw my own icon, the icon doesn't show.

My drawing code (simplified):

public struct IconTestView: View {
  private func makePath(size: CGSize) -> UIBezierPath {
    let path = UIBezierPath()
    path.move(to: CGPoint(x: size.width * 0.5, y: 0))
    path.addLine(to: CGPoint(x: size.width, y: size.height * 0.5))
    path.addLine(to: CGPoint(x: size.width * 0.5, y: size.height))
    path.addLine(to: CGPoint(x: 0, y: size.height * 0.5))
    path.addLine(to: CGPoint(x: size.width * 0.5, y: 0))
    path.close()

    return path
  }

  public var body: some View {
    GeometryReader { geo in
      Path(
        makePath(size: geo.size).cgPath
      )
      .stroke(
        .white,
        style: StrokeStyle(lineWidth: 2.0, lineCap: .round, lineJoin: .round)
      )
      .frame(width: geo.size.width, height: geo.size.height)
    } /// geo
    .frame(idealWidth: .infinity, maxWidth: .infinity, idealHeight: .infinity, maxHeight: .infinity)
  }
}

My widget then looks like this:

  var body: some View {
    Label {
      Text("Hello world")
    } icon: {
      IconTestView()
    }
  }

The IconTestView() draws a diamond shape inside .accessoryCircular just fine, but nothing is drawn in .accessoryInline when I return the above label.

Is this scenario just not supported (= I can only pick the icon out of SF symbols), or is there a way to do this?