How to disable textfield without making it grayed out?

like having .disabled without graying it out?

That would be confusing for the user. It is very important to have a consistent.

I tried something. Let me know if that's what you are looking for:

struct ContentView: View {
    @State private var theField: String = ""
    @State private var disabledField = true
    @State private var prompt: String = "disabled"
    @FocusState private var focusedField: Int?

    var body: some View {

            TextField(prompt, text: $theField)
                .frame(width: 200, height: 30)
                .disabled(disabledField)
                .focused($focusedField, equals: 1)
            
                .overlay(   // so the doubletap will be handled, even though textFied is disabled
                    RoundedRectangle(cornerRadius: 4)
                        .stroke(Color.gray, lineWidth: 1) // just to see, color can be set to bg or white
                        .offset(x: -5, y: 0)
                        .onTapGesture(count: 2) {
                            prompt = "Enter"
                            disabledField = false
                            focusedField = 2 // any value ≠ 1: to get the cursor appear when set to 1
                            DispatchQueue.main.asyncAfter(deadline: .now() + 0.01) { // delay to sequence focus changes and get cursor appear
                                focusedField = 1
                            }
                        }
                )
    }
}

You can set the color of the prompt so that it does not appear dimmed

            TextField(prompt, text: $theField, prompt: Text(prompt).foregroundColor(.blue))

Have you explored using @FocusState to programmatically control the focus of the TextField? The point here is that a TextField needs to be in focus to accept input, and a user can move focus to the TextField by tapping on it.

You could also use the binding to a focusState to determine the conditions and programmatically move focus.

You should check out FocusState and Focus Cookbook sample projects for example on how to control focus programmatically.