@nicolec5631060 there's a way to implement customisation to ensure client libraries could enable async, https://github.com/nateyolles/aem-clientlib-async.
Currently how are you including Tealium as a DTM to your webpage?
From my knowledge, a DTM script is nothing but a CDN absolute path, you can easily insert this block of code, within the <head>,
<script src="https://polyfill.io/v3/polyfill.min.js?features=IntersectionObserver" async></script>
