MAUI - Access XAML element from a different class code behind

I'm working on my first MAUI app. It consists of two screens, switchable via a tab control.

Now to my issue - I have page MainPage.xaml with MainPage.xaml.cs and also AboutPage.xaml with AboutPage.xaml.cs.
Is there a way how to access an element of AboutPage.xaml from MainPage.xaml.cs?

My goal is, when I press a button on MainPage.xaml, I want to write a text on AboutPage.xaml, so that it's there when user switches to AboutPage via the tab.

In my AboutPage.xaml, I have

<Label 
    x:Name="textBox1"
    x:FieldModifier="public"
    Text="This a test app." />

Then, in MainPage.xaml.cs I would like to do something like

 private void OnCounterClicked(object? sender, EventArgs e)
 {
     count++;
     changeAboutText();
 }

public void changeAboutText()
{
    var aboutPage = new AboutPage();
    aboutPage.textBox1.Text = "hello";
}

This does not say any errors when building, but it does not change the text to "hello" on the AboutPage.

Any ideas?

Thanks a lot in advance for any hint!

BR, Martin