Ubuntu 18.04 "W: Conflicting distribution" from ppa

I have attempted to install the ppa using the file:

$ cat /etc/apt/sources.list.d/plexmediaserver.list 
deb https://downloads.plex.tv/repo/deb/ public main

Now whenever I run "sudo apt update" I get the line:

W: Conflicting distribution: https://downloads.plex.tv/repo/deb public InRelease (expected public but got )

I tried following the advice from another post of adding "./" before public
https://forums.plex.tv/discussion/273920/w-conflicting-distribution-https-downloads-plex-tv-repo-deb-public-inrelease-expected-public
But I get the following:

Err:8 https://downloads.plex.tv/repo/deb ./public Release
  404  Not Found [IP: 104.18.157.41 443]
Reading package lists... Done                      
E: The repository 'https://downloads.plex.tv/repo/deb ./public Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

Does something need to be updated for bionic?