Go to https://www.naturalearthdata.com/downloads/110m-cultural-vectors/
Download "Admin 0 – Countries" / "Download countries"
Go to https://mapshaper.org/
Upload all files from ZIP.
Then Export GeoJSON.
Save as /countries.json
Go to https://www.naturalearthdata.com/downloads/110m-cultural-vectors/
Download "Admin 0 – Countries" / "Download countries"
Go to https://mapshaper.org/
Upload all files from ZIP.
Then Export GeoJSON.
Save as /countries.json