If you want to avoid traversing subviews & potentially dangerous hacks in general, what I've done is set the badge's background colour to clear and used a styled bullet point to appear as a badge:
tabBarItem.badgeValue = "●"
tabBarItem.badgeColor = .clear
tabBarItem.setBadgeTextAttributes([NSAttributedStringKey.foregroundColor.rawValue: UIColor.red], for: .normal)
This seems more future-proof than the other answers.
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