Adding custom button on top of the webview

Hi, I tried to add close button on top of the webview. As I cannot use unity UI canvas objects on top of the webview, I tried editing js code this way:

var buttonSize = 0.417f;
_webViewObject.EvaluateJS($@"
(function() {{
var button = document.createElement('button');
button.style.position = 'fixed';
button.style.left = '{buttonSize / 2f}in';
button.style.top = '{8}px';
button.style.zIndex = 2147483647;
button.style.width = '{buttonSize}in';
button.style.height = '{buttonSize}in';
button.style.backgroundColor = 'transparent';
button.style.color = '#413e3e';
button.style.border = 'none';
button.style.borderRadius = '50%';
button.style.fontSize = '24px';
button.style.cursor = 'pointer';
button.style.display = 'flex';
button.style.alignItems = 'center';
button.style.justifyContent = 'center';
button.style.textAlign = 'center';

  var img = document.createElement('img');
  img.src = 'https://fonts.gstatic.com/s/i/materialiconsoutlined/close/v1/24px.svg';
  img.style.filter = 'invert(100%) sepia(100%) saturate(0%) hue-rotate(0deg) brightness(0%) contrast(100%)';
  img.style.width = '100%';
  img.style.height = '100%';
  img.style.objectFit = 'cover';
  img.style.borderRadius = '50%';
  img.style.backgroundColor = 'transparent';
  img.style.color = '#413e3e';
  button.appendChild(img);

  button.onclick = function() {{
    {onClickFunction};
  }};
  document.body.appendChild(button);
}})()");

This function is called when the webview is loaded(ld). In Android it works fine, I see the close button with the correct icon. But in IOS devices, the close button does not even show. So what can affect to it in IOS devices? And maybe there are better ways to add custom button on top of the webview?

Start with the EvaluateJS snippet in the issue and the ld webview-loaded callback, then compare the documented Unity WebView behavior on Android and iOS. Done means identifying why the injected button is absent on iOS and documenting or implementing a supported way to place a close button above the webview.