In this older Floatplane recruitment video, Luke mentions it's on a mean stack.
Not sure how much has changed at that point, but probably good starting point nevertheless.
Vessel account: Jaychu
https://www.vessel.com/videos/Yj4PbcgKj
https://www.vessel.com/videos/G-DUjgUyY
Social media shares:
https://twitter.com/jayxchu/status/580595664159174656
https://www.facebook.com/SourceOfChaos/posts/390932527753015