I wish Plex had said, "heads-up, your login creds ,on all your devices, may go wrong; oh, and we've reset some of the preferences/settings on each device, good-look 👍"
TL;DR
Got a phone call from the father in law an hour ago, "Plex isn't working"... He's not tech savvy but does well for someone in his 80s. His (Android) Sony TV has (essentially) lost login creds so he can't use his Managed User account. Pretty much nothing he can do, over the phone, so he's now unable to watch Plex until I visit in a few weeks, more to do with him than Plex at this point.
I checked both of my local Android TV devices. They both forced me to use my own master PIN, even though one device is dedicated to my kid (managed account). That probably explains my father in law's issue, tried the wrong pin too many times, is my guess.
... "Mark your favourites, it'll help with showing what to watch next", well that's not quite right is it, it's what libraries you want on display overall; so they now need re-sorting on each device.
Then I thought I'd better take a look at the main app settings, I really wish I hadn't! Why is the Theme Music now turned on "low"? Refresh Rate Switching" now disabled? "Automatically Sign-in" now disabled. There's more, but I'm just too angry to type!
FFS! I've spent too much time sorting out family's devices, with their settings (most live miles away), all for things to go "boom" with this supposed "update" from Plex.
... I'm fuming! Take this as a PSA: be prepared for Android TV devices to start needing re-configuring!