https://launchpad.net/~nginx

# add-apt-repository ppa:nginx/stable
# apt-get update
# aptitude install nginx

# apt-get update
# aptitude install nginx

# service nginx status
● nginx.service - A high performance web server and a reverse proxy server
   Loaded: loaded (/lib/systemd/system/nginx.service; enabled; vendor preset: enabled)
   Active: active (running) since Sat 2019-04-06 14:50:15 CEST; 9min ago
     Docs: man:nginx(8)
  Process: 8408 ExecStop=/sbin/start-stop-daemon --quiet --stop --retry QUIT/5 --pidfile /run/nginx.pid (code=exited, status=0/SUCCESS)
  Process: 8826 ExecStart=/usr/sbin/nginx -g daemon on; master_process on; (code=exited, status=0/SUCCESS)
  Process: 8820 ExecStartPre=/usr/sbin/nginx -t -q -g daemon on; master_process on; (code=exited, status=0/SUCCESS)
 Main PID: 8828 (nginx)
    Tasks: 2 (limit: 2319)
   CGroup: /system.slice/nginx.service
           ├─8828 nginx: master process /usr/sbin/nginx -g daemon on; master_process on;
           └─8830 nginx: worker process

Apr 06 14:50:15 xxx systemd[1]: Starting A high performance web server and a reverse proxy server...
Apr 06 14:50:15 xxx systemd[1]: nginx.service: Failed to parse PID from file /run/nginx.pid: Invalid argument
Apr 06 14:50:15 xxx systemd[1]: Started A high performance web server and a reverse proxy server.

# netstat -anptu
Aktive Internetverbindungen (Server und stehende Verbindungen)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN      8828/nginx: master
tcp6       0      0 :::80                   :::*                    LISTEN      8828/nginx: master

Als root ausführen:

# apt-get update
# apt-get install software-properties-common
# add-apt-repository universe
# add-apt-repository ppa:certbot/certbot
# apt-get update
# apt-get install python3-certbot-nginx

Folgt.