Even slight main thread congestion causes Alert to miss dismissals

For this sample project just move out the counter Text to standalone View and pass Binding:

struct CounterView: View {
    @Binding var counter: Int

    var body: some View {
        Text("Counter: \(counter)")
            .font(.caption)
    }
}

Then replace this:

Text("Counter: \(counter)")
    .font(.caption)

With:

CounterView(counter: $counter)

P.S. To understand the problem, add in the body:

var body: some View {
    let _ = Self._printChanges()
    ...

You're missing the point, the problem isn't with the counter, that was just to demonstrate the problem with Alert.

It only happens with that particular Alert modifier, with other ones it works fine.

You are right, it is just a workaround for this particular case, allowing to avoid constant calls to the body and Alert reinitializations.

It turns out that when calling body, when reinitializing Alert, the connection with the AlertController, which is displayed, is somehow lost. Which leads to this problem.

But it is unlikely that we need to wait for this problem fixes, since Alert is deprecated.