I thought that was only the case for managed users where the admin had to set the sign in automatically option. I am pretty sure in the past it worked that if you had your own Plex account (as in the case for the OP), you would be able to set that option. It was only with managed users that the admin needed to set that option for it to apply for them (and it had no bearing on the users that had an actual Plex account).
Edit: Also, if that is the case the support article (at least for the Android TV settings) does not make it clear that is how it works. Furthermore, the support article doesn’t make it clear that needs to be done for managed users (at a minimum), though I can’t remember if I had found that information in the forum or on one of the support pages when I ran into that issue.
The setting is not for the user. It is a device setting. That setting is to automatically sign in as the last user bypassing any PIN restrictions. So if the Uncle Bob user was last signed in, the next time you turn on the app, it will use Uncle Bob’s account again without asking for his PIN.
It is a setting per device in that if it is on for one person it is on for everyone. The setting should be there for all users in home except managed. Are on my Androids and the web browser app. Not aware of any changes there.
Thanks for jumping into the thread @BigWheel and helping out with this. @anon18523487, just want to make sure I didn’t come across as a jerk in my reply, as that was not my intention. I was just pretty sure the option was supposed to be visible to all but managed users in a home, as BigWheel confirmed in his one reply in this thread and the thread I linked.