AllTrails couldn't find "Shanghai", but my subscription lapsed years ago. Gaia is what I use on the ground but it's about where you are, not about where the trail is.....but I'm finding one of the ancient roads. A bit of a mess but it looks viable.
GPS works properly in China, it's just the maps are a lie. If someone made a .gpx of a trail someone else could use it. The line is pointy and a bit disjoint so I suspect someone uploaded points to Open Street Map.
