Here is my code in c# that works on Windows. Event separates visible and hidden characters, so I can handle both:

    public void TxtScanPlace_PreviewTextInput(object sender, TextCompositionEventArgs e)
          {
                keyDiff = DateTime.Now.Millisecond;

                if (e.Text.Length > 0)
                {
                    SCANTXT += e.Text;
                    SCANTXTRAW += e.Text;
                }

                else if (e.ControlText.Length > 0)
                {
                    SCANTXT += "\u001d"; // Ubacivanje kontrolnog koda
                    SCANTXTRAW += e.ControlText;
                    controlCode++;
                }

                e.Handled = true; // Sprečava unos karaktera direktno u TextBox

        }

Here is my code in MAUI where entry not shows hidden chars, entry just shows visible charactes, but I need hidden like char29 or group separator:

public async void OnEntryCompleted(object sender, EventArgs e)
{
    if (sender is Entry entry)
    {
        string scannedData = entry.Text; 

        if (!string.IsNullOrEmpty(scannedData))
        {

            SCANTXT = scannedData.Replace("\u001D", "[GS]");
            SCANTXTRAW = scannedData; 

            Console.WriteLine($"SCANTXT: {SCANTXT}");
            Console.WriteLine($"SCANTXTRAW: {SCANTXTRAW}");
        }

        //await ProcessCodeInput();

        SCANTXT = string.Empty; 
        entry.Text = string.Empty; 
    }
}