There are several ways to handle and mitigate this potential problem.
<script async src="https://url.com/jsfile.js"></script>
– Be careful!
Be very careful when implementing this solution, as with multiple scripts loaded asynchronously, the order that they are loaded onto the page will essentially be randomised. A typical example will be a script that requires jQuery being loaded before jQuery is loaded, causing an error being thrown. The best practice solution here is to bundle scripts appropriately so that those that have requirements will not be loaded separately from the required scripts.
Moving scripts to the footer
The other, much simpler solution is to move the scripts to the bottom of the page. This is so simple as we know that the higher a script on a page, the less of the pages UI that is built and shown before the script is downloaded and run. Therefore if the script is at the bottom of the page, all of the page elements that are above it are loaded in before it is. This guarantees that the scripts won’t block substantial amounts of UI rendering. This is a quick and simple solution, but it will not improve your page speed score (especially on mobile) to the degree that a properly implemented bundled asynchronous script setup will do.