We are about to officially launch Cleanfox : www.cleanfox.io
The issue that Google indexes the website only in English and when I look at the search results on Google.fr, the indexed content is in English.
I have gone through all the required stuff on both the Google Webmaster Console adding both FR and EN. I added hreflang attributes in both meta and links (the two links that lead to another language)... But nothing happens, all the content is just indexed in English.
The problem is that you are using the same URL for both languages (see answer with more details).
Furthermore, with rel-alternate+hreflang you should point to translations of the current document, but you always seem to point to /en//fr (which then redirects to /). So for example, the following declaration on https://www.cleanfox.io/forest is wrong:
<link rel="alternate" hreflang="fr" href="https://www.cleanfox.io/fr"> <link rel="alternate" hreflang="en" href="https://www.cleanfox.io/en">
Neither /fr nor /en is a translation of /forest.