How I've been installing and updating the YouTubeTV plugin on Ubuntu Server 16.04...
Download the latest tar.gz release of the plugin from the author's GitHub page here
Extract the file
tar -xvf v4.6.tar.gz
This will create the YouTubeTV.bundle-4.6/ folder. This needs to be placed in the Plex Plugins folder, the release number needs to be removed as well. I normally rename and the move but it can be done in one as follows
mv YouTubeTV.bundle-4.6/ /var/lib/plexmediaserver/Library/Application\ Support/Plex\ Media\ Server/Plug-ins/YouTubeTV.bundle/
The official Plex helpsheet says that you may need to reboot the server, but for me this worked with a refresh of the page.
To update the plugin I moved the folder in Plugins back to my home directory, then moved the new one in and refreshed the page.