<p>
<strong>Identifier:</strong> {Identifier}
</p>
<p>
<a target="_blank" rel="noopener noreferrer" href="https://survey123.arcgis.app/?itemID=1ef4616e6d004f93a9043b1813242e92;field:Site={Identifier}">Open Survey</a>
</p>
I think "&" instead of ";" should work:
https://survey123.arcgis.app/?itemID=1ef4616e6d004f93a9043b1813242e92&field:Site={Identifier}
you can also add "&callback=https%3A%2F%2Ffieldmaps.arcgis.app%2F" so after you finished your edits in Survey123 it automatically jumps back to field maps, more infos you can find here Callback URLs! How do I get this thing to actuall... - Esri Community