Finally nailed it. I installed Plex Media Server on a remote host and after visiting the http://REMOTE_HOST_IP:32400/web I had no add server option.
I ended up with port forwarding to the remote host
ssh -L 32400:raspi:32400
To be able to add server I had to connect to localhost http://localhost:32400/web/index.html#!/setup
More info about troubleshooting remote access is at https://support.plex.tv/articles/200931138-troubleshooting-remote-access/