Actually, I have xau as well.Thanks for the reply! This makes sense. I guess having the XAU in my service provider version may be due to setting up the device with a deactivated sim. If anyone with a T-Mobile locked F926U device could verify weather or not they have the XAU in service provider version (see screenshot) it would be greatly appreciated! Trying to avoid resetting my device to find out
My phone was set up at t-mobile, but they had to get me a 5g Sim card because my previous phone only had LTE.
I'm 99% sure the XAU just means it's a multi CSC firmware that doesn't set a specific region when firmware is flashed. Instead using the Sim to check region for Ota updates.
Which as you said could be due to being set up without a Sim card, but also could be just how the fold 3 is if it's a universal CSC partition. That would require someone to chime in that had a proper Sim card in the phone during setup.
Normally a phone pings Samsung's servers when booting after firmware flash and sets the region to whatever server location is closest, as well as inferring carrier specific CSC from that region.
That generally would mean that you couldn't get Ota updates from someplace that isn't your region. (say you were overseas)