URL Request Transform
New Feature
Looking at the v10 API I cannot find a replacement for the FileSource Resource Transform Callback: https://docs.mapbox.com/android/maps/api/9.5.0/com/mapbox/mapboxsdk/storage/FileSource.ResourceTransformCallback.html The Observable plugin might provide this feature but I cannot see a way or example to modify the request.
Why
Other Tile providers such as HERE require custom headers on requests https://developer.here.com/documentation/vector-tiles-api/dev_guide/topics/examples/mapbox.html
It was added to GL JS on numerous requests. https://github.com/mapbox/mapbox-gl-js/pull/5021
Anything new on this request? I'm having the same issue. See my post on StackOverflow. Thanks :-)