V4 Popup on SVG element

Is there any way to anchor a popup to an element in an embedded SVG such as a path or rect element?

The anchor option can take a string with the id of the element it is “anchored to”. If you assign an id to the rect inside the svg, that same id should work for the popup.

$('#my-popup').mobiscroll().popup({
  anchor: '#myRecID',
});

Then in your svg:

<svg>
  <rect id="myRecID" x="10" y="10" width="100" height="50" />
</svg>