Hi again!
We have discussed the geojson for Unity in this post https://itch.io/t/643400/geojson-export-for-unity3d-integration
After building the first version of the importer, I haven't tried to import/export any map.
Today, I've tried to export a new map and failed:( It seems that json Feature objects for new maps don't have "geometry" (it is totally required by the standard https://tools.ietf.org/html/rfc7946#section-3.2)
Have the export code was updated somehow?