I have this phone (unlocked) and I'm attempting to connect to AT&T network, unsuccessfully. I read up on this and it appears AT&T has whitelisted which models can connect. Some pundits tell there is AT&T firmware for this phone ... which I haven't found.
Can anyone comment, please, am I on the right path? Can this phone be connected to AT&T?

Bad news. Found the firmware, using latest odin tool I get protocol error. Search reveals just this model does not flash with odin.
I have a Mac somewhere, I use it if Linux fails, happens very seldom. I will set up that Mac now and see if it is any better.

I have a Samsung A-10 here in Ireland. No need to adjust your set, it should work fine. Is there a sim in it?

AFAIK, it's got the same camera and pcb as one of their flagship phones. So my cpu is an Exynos 8 core, but at 1.3GHz. Other sensors (e.g. compass) are awol. But it sold for ¼ of the price.

I'm sure AT&T accepts global version, but they wont let phones with US T-Mobile firmware to connect.