What about PlexKodiConnect and PleXBMC?
(see below for a more detailed explanation of the differences)
Both of them serve different purposes, just like this add-on. The goal of this add-on is essentially to give you a full, rich Plex app experience (on top of Kodi) that uses the powerful Kodi backend. If you're just looking to allow Kodi to connect with your Plex Media Server, both the PlexKodiConnect and PleXBMC unofficial add-ons can allow you to do that, it just won't be as rich and immersive a Plex experience as our official Plex for Kodi add-on provides. We do not provide support for those unofficial add-ons.
We presently are only focused on supporting Confluence and Estuary, the two default skins, during the current development cycle. We will evaluate supporting others that are in the repo once we've reached feature complete.
You need to install and setup a subtitle downloader in Kodi, after that enable Download Subtitles in Settings and an OSD option will appear when playing back a video that will automatically download subtitles on demand. Currently this is non persistent which is a known issue.
In Kodi, Navigate to: Settings → System → Standard at the bottom. Change this to Expert. Scroll down to Allow passthrough and click on it. Now enable which options your receiver supports (AC3, DTS, TrueHD. etc) and this will work inside Plex for Kodi as well.
Start Plex on Kodi Startup
Under Settings → Advanced → Enable Start Plex on Kodi Startup to automatically have Plex load when Kodi is started.
Can't connect to my.plexapp.com/plex.tv
Be sure to make sure your ad-blockers are disabled in your network. Pi-hole's are a common issue, also on Android, adaway could have rules that need to be whitelisted. As a workaround, test using Google DNS: 184.108.40.206. If that works, you know something in your network needs to be changed.