This is still a bug, even though the topic is closed: Plex w/ managed users on Apple TV requires selecting the user each time - #11 by Sylvesterke
If you have a Managed User account you’d like to automatically be used on your Apple TV (and bypass the account switcher prompt every time the app is launched), you’ll need to uninstall and reinstall the app in order for the Automatic Sign In option to show up in your settings (under your admin account).
