I have the same problem and after wasting a lot of time, it turns out the keyboardShortcut modifier appears to be bjorked when running using the "My Mac (Designed for iPad)" option.
To get around it, I created the following View extension:
extension View {
@ViewBuilder func keyboardShortcutHack(_ key: KeyEquivalent, modifiers: EventModifiers) -> some View {
/* #if targetEnvironment(macCatalyst) and os(macOS) don't work when running using the "My Mac (Designed for iPad)" */
if ProcessInfo.processInfo.isiOSAppOnMac {
self
}
else {
self.keyboardShortcut(key, modifiers: modifiers)
}
}
}
I did file this via the Feedback Assistant with Apple.