iOS document based app problem running on Mac (Designed for iPad)

Please can somebody help me? I have a document-based iOS in the App Store (iNetWorth). I was able to run it on my M1 Mac Mini as a Mac (Designed for iPad) app without any issues until macOS 15. So, I created a simple test app based on a TabView to try and find out why I cannot get iNetWorth to run successfully on my Mac.

The issue is that when TabViewApp.swift file looks like this:

import SwiftUI
 
@main
struct TabViewApp: App {
    var body: some Scene {
        /*WindowGroup {
         ContentView()
         }*/
        DocumentGroup(newDocument: TextFile()) { file in
            ContentView(document: file.$document)
        }
    }
}

TabView fails to load the ContentView() - in Xcode 16.2 running on macOS 15.3.2. On opening, the TabView app prompts the user to open a new or existing file normally but it then opens a window that is empty, apart from a Documents button and a label displaying the filename with a dropdown menu (Duplicate, Move, Rename..., Export As…).

If the @Binding var document: TextFile line is removed from the ContentView() and the TabViewApp.swift file is changed to:

import SwiftUI
 
@main
struct TabViewApp: App {
    var body: some Scene {
        WindowGroup {
         ContentView()
         }
        /*DocumentGroup(newDocument: TextFile()) { file in
            ContentView(document: file.$document)
        }*/
    }
}

the TabView app loads and displays the ContentView() correctly.

Both versions of TabView, when running in Xcode on My Mac (Designed for iPad), produce these warnings:

CLIENT: Failure to determine if this machine is in the process of shutting down, err=1/Operation not permitted LSPrefs: could not find untranslocated node for <FSNode 0x6000013901a0> { isDir = ?, path = '/private/var/folders/3f/8788c4dj50q050_4wg9fssbr0000gp/X/518B55E1-0EC4-5D84-9202-4E44410EB249/d/Wrapper/TabView.app' }, proceeding on the assumption it is not translocated: Error Domain=NSPOSIXErrorDomain Code=1 "Operation not permitted" LSPrefs: could not find untranslocated node for <FSNode 0x6000013901a0> { isDir = ?, path = '/private/var/folders/3f/8788c4dj50q050_4wg9fssbr0000gp/X/518B55E1-0EC4-5D84-9202-4E44410EB249/d/Wrapper/TabView.app' }, proceeding on the assumption it is not translocated: Error Domain=NSPOSIXErrorDomain Code=1 "Operation not permitted" LSPrefs: could not find untranslocated node for <FSNode 0x6000013901a0> { isDir = ?, path = '/private/var/folders/3f/8788c4dj50q050_4wg9fssbr0000gp/X/518B55E1-0EC4-5D84-9202-4E44410EB249/d/Wrapper/TabView.app' }, proceeding on the assumption it is not translocated: Error Domain=NSPOSIXErrorDomain Code=1 "Operation not permitted" LSPrefs: could not find untranslocated node for <FSNode 0x6000013901a0> { isDir = ?, path = '/private/var/folders/3f/8788c4dj50q050_4wg9fssbr0000gp/X/518B55E1-0EC4-5D84-9202-4E44410EB249/d/Wrapper/TabView.app' }, proceeding on the assumption it is not translocated: Error Domain=NSPOSIXErrorDomain Code=1 "Operation not permitted”

However, the document-based version of TabView also displays these warnings:

cannot open file at line 49450 of [1b37c146ee] os_unix.c:49450: (2) open(/private/var/db/DetachedSignatures) - No such file or directory

I suspect that the lack of the DetachedSignatures file is the root cause of the ContentView() not being loaded but I cannot find out how to generate a DetachedSignatures file. Adding an empty DetachedSignatures file or directory to /private/var/db/ does not help.

Has anyone else experienced this problem (and maybe found a solution)? Should I raise it as a bug via Feedback or am I missing something obvious? Thanks!