Legacy Segmented Control style?

What don't you like ? Rounded corners ?
If so, could you try to subclass UISegmentedControl as follows:

Code Block 
class SquareSegmentedControl: UISegmentedControl {
     
     override func layoutSubviews() {
          super.layoutSubviews()
          layer.cornerRadius = 0
          for view in self.subviews {
               view.roundCorners(corners: UIRectCorner.allCorners, radius: 0)
          }
     }
}

If there are other points which cause problem, have a look here.
https ://medium. com/flawless-app-stories/ios-13-uisegmentedcontrol-3-important-changes-d3a94fdd6763

If that's not enough, you could define your complete custom segmentedControl.

But note that unless you have a compelling reason to do so, it's not a great idea to go against standard control design. Very rapidly, your app will look outdated and surprise the users.