Good news on the alternatives offered before. Tried yesterday both of them:
1) On the repo called “Don’t Panic” (link provided above by @greebs777) once added to your sources you’ll be able to install what looks is an old Plex addon version but is working flawlessly with the latest Kodi v20. So you’ll have 2 Plex addons installed (the official/useless for now) and the alternative (working addon).
2) The other video addon is called Composite (an alternative Plex client, available on the official Kodi repo), this one basically allows you to browse (as folders) the different “videos” available or served by the Plex server you’re connecting to, so also as an alternative could be a temporary side solution.
Beware the 2nd alternative, is still affected by several issues as reported by users on the Kodi forum.
Thanks again @greebs777 for these alternatives, specially on these moments, when the official addon is useless on Kodi 20. 
