Are there any options for indexing a site which uses the React JavaScript framework for front end display? E.g. there’s no content / html generated except via JavaScript
The short answer is no - Funnelback doesn’t process Javascript and will get a view of the website similar to what you would see if you visited the site with Javascript disabled.
You might be able to supply a version of the page that can be indexed by the Funnelback but you’d also need to be request each of these pages directly (e.g. from a sitemap.xml) and have the correct information returned