Capture the URL in a variable and use it in your code using concatenation.
var url = document.location.href;
gtag('event', 'conversion',{
'allow_custom_scripts': true,
'u1': url,
'send_to':'something'
});
For the noscript tag it will not work as DTM require javascript to work so if there is noscript it means there is no javascript allowed so it will never run.