I've done as much research as I can and I'm still confused. I bought a phone that shows the AT&T logo on boot but I've always been on T-Mobile's network, so it's never updated since Android 8.0.

I would like to install a firmware that allows it to automatically update from here on out.

1. Should I install the TMB region firmware since that's the network I'm on?
2. Or if I install XAS or USC region firmware will it auto update from here on out?

In Version, my CSC shows G960UOYN3ARG8

And in Service Provider SW ver.

When I search that CSC model I find region code USC.

Any help is greatly appreciated. I'm lost on this.
Thank you.