How do I configure automatic subtitles for managed users?

@sonivex said:
Automatically select audio and subtitle tracks: checked
Prefer audio tracks in: English
Subtitle mode: Always enabled
Prefer subtitles in: Português (Brasil)

The above settings are individual for every user.
Switch to ‘become’ your managed user in the web app

then in the same menu click on ‘Account’ and make the desired selections under
‘Audio & Subtitle settings’
(don’t forget to fill the checkbox at the top)

(‘Regular’ plex users (i.e. ‘Friends’) make their own selections in the properties of their plex accounts directly on https://plex.tv/users/profile )