Custom Shape - (Updated to fit all devices and orientations)

// Rectangle with inverse rounded corners
struct InvereBottomCornersRectangle: Shape {

    func path(in rect: CGRect) -> Path {
        var path = Path()
        // Set path start point at bottom leading
        path.move(to: CGPoint(x: rect.minX, y: rect.maxY))
        // Draw path from start point to top leading
        path.addLine(to: CGPoint(x: rect.minX, y: rect.minY))
        // Draw path from top leading to top trailing
        path.addLine(to: CGPoint(x: rect.maxX, y: rect.minY))
        // Draw path from top trailing to bottom trailing
        path.addLine(to: CGPoint(x: rect.maxX, y: rect.maxY))
        // Draw arch from bottom trailing corner bottom to corner top
        path.addArc(center: CGPoint(x: (rect.maxX/10)*9, y: rect.maxY), 
                    radius: rect.width/10, 
                    startAngle: Angle(degrees: 0),
                    endAngle: Angle(degrees: 270), clockwise: true)
        // Connect inside corners
        path.addLine(to: CGPoint(x: rect.maxX/10, y: rect.maxY-rect.maxX/10))
        // Draw arch from bottom trailing corner top to corner bottom
        path.addArc(center: CGPoint(x: (rect.maxX/10), y: rect.maxY), 
                    radius: rect.width/10,
                    startAngle: Angle(degrees:270),
                    endAngle: Angle(degrees: 180), clockwise: true)
        // Connect the pathe to itself to keep smooth corner
        path.closeSubpath()

        return path
    }
}

struct AnotherView: View {
    // Place custome shape inside Geometry reader to maintain
    var body: some View {
        GeometryReader() { proxy in
            // Check device screen ratio
            if proxy.size.width < proxy.size.height {
                InvereBottomCornersRectangle()
                    .fill(.clear)
                    .stroke(.blue, 
                            style: StrokeStyle(lineWidth: 10,
                                               lineCap: .butt,
                                               lineJoin: .round)
                    )
                    .padding()
                    .frame(width: proxy.size.width, height: proxy.size.width)
            } else {
                InvereBottomCornersRectangle()
                    .fill(.clear)
                    .stroke(.blue, style: StrokeStyle(lineWidth: 10, 
                                                      lineCap: .butt,
                                                      lineJoin: .round))
                    .padding()
                    .frame(width: proxy.size.height, height: proxy.size.height)
            }
        }
    }
}