@Tomasz_Kusmierz Hello again.
I’m fairly sure this auto update is dependant on having your Plex server rockon registered, ie via a Plex user account. That way the startup update scripts in the container can validate the version of the software appropriate to your account, ie if your Plex account has a Plex pass associated with it or not. It can then check and download the appropriate version. Otherwise it sits at whatever the default version was when first installed.
Also from:
https://hub.docker.com/r/linuxserver/plex/
we have:
"Note about updates, if there is no value set for the VERSION variable, then no updates will take place.
For new users, no updates will take place on the first run of the container as there is no preferences file to read your token from, to update restart the Docker container after logging in through the webui
IMPORTANT NOTE:- YOU CANNOT UPDATE TO A PLEXPASS ONLY VERSION IF YOU DO NOT HAVE PLEXPASS
latest: will update plex to the latest version available that you are entitled to.
public: will update plexpass users to the latest public version, useful for plexpass users that don’t want to be on the bleeding edge but still want the latest public updates.
specific-version: will select a specific version (eg 0.9.12.4.1192-9a47d21) of plex to install, note you cannot use this to access plexpass versions if you do not have plexpass."
(minor formatting edit required around “specific-version” within quoted text)
Hope that helps.