Here is a configuration of a reverse proxy that serve the content of other domain. Used to serve in zulu the content of radio.clubs.etsit.upm.es with the domain ea4rct.org:

server {
	server_name ea4rct.org;
	listen 443 ssl http2 default_server;

	add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always;

	ssl_certificate /etc/letsencrypt/live/ea4rct.org/fullchain.pem;
	ssl_certificate_key /etc/letsencrypt/live/ea4rct.org/privkey.pem;

	location / {
		proxy_pass https://138.4.51.66:443;
		proxy_set_header X-Real-IP $remote_addr;
		proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
		proxy_set_header X-Forwarded-Proto $scheme;
		proxy_set_header X-Forwarded-Port 443;
	}
}