In the same theme as this post: ios13 UIPopoverViewController showing UITableViewController - Safe Area problems / Missing parts of table
But in my case, it is not especially a UITableViewControllerany any View Controller in a popover on the iPad has the same issue since iOS13.
I have no problem with overlapping content, just the border.
let popoverContent = self.storyboard!.instantiateViewController(withIdentifier: controllerName) as! SelectSceneViewController
popoverContent.preferredContentSize = CGSize(width: 700,height: 500)
let nav = UINavigationController(rootViewController: popoverContent)
nav.modalPresentationStyle = UIModalPresentationStyle.popover
nav.navigationBar.barStyle = navbarStyle
nav.view.layer.cornerRadius = 10
nav.view.layer.borderColor = UIColor.white.cgColor
nav.view.layer.borderWidth = 2
let popover = nav.popoverPresentationController
popover?.sourceView = button
popover?.sourceRect = button.bounds
self.present(nav, animated: true, completion: nil)