However, all these tiles contain the same local-language labels, corresponding to the name tag in OSM rather than tags like name:en or name:de. The same is true for any other language selection:
If I omit the _, which is supposed to be the local fallback, I always get a 404 error no matter how many times I retry:
The old Toolserver tile server worked for all the Wikimedia languages. I had to switch the Vietnamese Wikipedia’s OSM gadget to use tile.openstreetmap.de and would like to hook it up to WMF Labs once its language support is built out.