Attempts to use gisco_get_countries to get a world shape return this error:

HTTP Status Code: 503 - Service Unavailable

url
https://gisco-services.ec.europa.eu/distribution/v2/countries/geojson/CNTR_RG_10M_2020_4326.geojson not reachable.

Please download manually. If you think this is a bug please consider opening an issue on https://github.com/ropengov/giscoR/issues
Returning NULL