Presents a modal view with the "over current context" style in SwiftUI.

View+OverCurrentContext.swift

import UIKit
import SwiftUI

fileprivate var currentOverCurrentContextUIHost: UIHostingController<AnyView>? = nil

extension View {
    
    public func overCurrentContext(
        isPresented: Binding<Bool>,
        showWithAnimation: Bool = false,
        dismissWithAnimation: Bool = false,
        modalTransitionStyle: UIModalTransitionStyle = .crossDissolve,
        modalPresentationStyle: UIModalPresentationStyle = .overCurrentContext,
        afterDismiss: (() -> Void)? = nil,
        content: () -> AnyView
    ) -> some View {
        if isPresented.wrappedValue && currentOverCurrentContextUIHost == nil {
            let uiHost = UIHostingController(rootView: content())
            currentOverCurrentContextUIHost = uiHost
            
            uiHost.modalPresentationStyle = modalPresentationStyle
            uiHost.modalTransitionStyle = modalTransitionStyle
            uiHost.view.backgroundColor = UIColor.clear
            
            let rootVC = UIApplication.shared.windows.first?.rootViewController
            rootVC?.present(uiHost, animated: showWithAnimation, completion: nil)
            
        } else {
            if let uiHost = currentOverCurrentContextUIHost {
                uiHost.dismiss(animated: dismissWithAnimation, completion: {})
                currentOverCurrentContextUIHost = nil
                afterDismiss?()
            }
        }
        
        return self
    }
}

//Example
struct TestView: View {
    @State var isPresented = false

    var body: some View {
        Button(action: {
            isPresented = true
        }, label: {
            Text("Show Modal")
        }).overCurrentContext(isPresented: $isPresented, content: {
            return AnyView ( //Important
                Text("This is the content of the modal view.")
            )
        })
    } 
}

Works, but it's a little flaky. Also, using AnyView is discouraged by Apple, because SwiftUI then has trouble building its view structure.
See this answer: https://stackoverflow.com/a/72580290/4846592