https://autio.com/ is similar - but obviously not open source, and more limited.
It seems like it could even tailor itself to what an individual user is interested in, and with AI - could turn more "dry" encyclopedia-type information into more compelling narratives. With some kind of route planning software, you could even pre-plan your trips ahead of time and select the things you're interested in.
Obviously not what you're building, but something related that's been clunking around in the back of my head for a while.