From the dev team:
Best option is to roll your own GeoJSON. First start by creating a static dataset that works how you want on the Perspective Map component (instructions at the end of the document I posted). We can separately deal with the problem set of dynamically generating the GeoJSON in the appropriate format (queries, scripting, transform, http binding, etc).
Resources to help:
https://mapbox.github.io/togeojson/
https://leafletjs.com/examples/geojson/
The Perspective Map component does not currently support “styles”. There is an active ticket (IGN-3354) to improve the map component, work not to start before 1Q22. If you email me a business case tied to customer examples I can get the support and requirement “ask” into the ticket. This ticket should include support for KML and GPX conversion to GeoJSON.