null objects

[SymbolixAU]

read as empty point (sf::st_point()) ?

I don't think there's a valid GeoJSON object for this. However, the sf object can be a Feature with a null geometry

sf <- sf::st_sf(geometry = sf::st_sfc(sf::st_point()))
sf_geojson(sf, simplify = FALSE)
# [1] "{\"type\":\"FeatureCollection\",\"features\":[{\"type\":\"Feature\",\"properties\":{},\"geometry\":null}]}"
# attr(,"class")
# [1] "json"