Copy the lodash CDN from here

In the Dittofi front-end builder, go to the Home Page settings ("Edit Page Settings"). In there you will see an option to add "Custom code" (it's the last option).

Since lodash is JavaScript, you will need to add a script tag with the cdn as the src attribute in the "Before tag" section and hit Save.

I.e., in the "Before tag" section, put in <script src="https://cdn.jsdelivr.net/npm/lodash@4.17.21/lodash.min.js"></script> and save.