macOS Server http(s) ports bound
Comment out listening ports at the beginning of the file /Library/Server/Web/Config/Proxy/apache_serviceproxy.conf

Kill parent httpd process which contains substring "/usr/sbin/httpd -D FOREGROUND -f /Library/Server/Web/Config/Proxy/apache_serviceproxy.conf". For listing these running proceses use ps -fax | grep apache_serviceproxy.conf, for example.