https://www.digitalocean.com/community/tutorials/how-to-secure-nginx-with-let-s-encrypt-on-ubuntu-20-04-es
sudo apt install certbot python3-certbot-nginx
sudo nano /etc/nginx/sites-available/example.com
...
server_name example.com www.example.com;
...
sudo certbot certonly --webroot -w /var/www/html/ -d tuSitio.ddns.net
#para validar configuracion
sudo nginx -t
#para recargar la nueva configuracion
sudo systemctl reload nginx
#para validar la actualizacion
sudo systemctl status certbot.timer
#para actualizar
sudo certbot renew --dry-run
#basado en
https://www.digitalocean.com/community/tutorials/how-to-secure-nginx-with-let-s-encrypt-on-ubuntu-20-04-es