Modify Viewport Meta Tag in WordPress & Divi for Accessibility

First Remove Viewport Meta Tag

function remove_et_viewport_meta() {
    remove_action( 'wp_head', 'et_add_viewport_meta' );
}
add_action( 'wp_head', 'remove_et_viewport_meta', 1 );

Add a New Viewport Meta Tag

function custom_add_viewport_meta(){
    echo '<meta name="viewport" content="width=device-width, initial-scale=1.0">';
}
add_action('wp_head', 'custom_add_viewport_meta');

Also install WP Accessibility