Hi @Nick-Hall and @jeff! I found this old thread by accident - I wasn’t notified by it - but I love the idea! Indeed I am still working on the web app (with the presumptuous title Gramps web app: https://github.com/DavidMStraub/gramps-webapp). In fact, having a frontend-agnostic REST API backend was one of the main ideas. Right now, I mostly use endpoints where I fetch huge dictionaries with all people, all places, …etc., and there are separate endpoints for media and thumbnails.
I would be happy to collaborate on an app-independent REST API backend.