Override CMS content for infinite scroll collection

I’ve cloned the Finsweet Infinite Scroll example and would like to override the data that is being displayed on the collection list - instead of loading content from CMS I’d like to load it from custom arrays with more than 10/20k items since that goes beyond free/paid Webflow limits.
Does anyone know how to use custom JS code to override the data source of a collection list so that it works for this case?