We've gathered "the essentials" of ways you can install your Alli snippet on your Typo3 website. Depending on the Typo3 version (and template used), here are the options you can try at the backend of your website.
Rendering Order of Assets in TYPO3
Source link: https://t3terminal.com/blog/add-css-js-typo3/
...And then just paste it for the appropriate option! That's it. Alli is now installed. =)