Mayhaps my Search-Fu is weak, because I can't find a list anywhere of AT&T carrier specific features.
Visual Voicemail... in the Playstore
HD calling... never had it, never felt a need for it, don't care
WiFi calling... see above, lol
Uber app forced on you... BITE ME AT&T.
Maybe faster updates? ... I've never been one to care. In fact I hate Pie and One UI so much I never took those or subsequent updates... never had any security or other issues on my Note 9
They disable Game Launcher too in favor of their own crap... or at least this used to be the case.
Anything I'm missing?