@alex Ah, ok. When I last read the instructions I thought it was pleroma-only, or moving in that direction.
Thanks for the link (and project!).
Based on my cursory examination of the nginx config you linked, it mounts the soapbox file root and then conditionally passes API queries back to the mastodon server. index.html seems to be overridden by soapbox routing.
Does the client-side JavaScript behave itself if I were to mount the index.html at /soapbox/index.html instead?