I was not able to activate service onto AT&T using my Fold with graphene (worked OK on Verizon). The mobile provider ported the number OK, but the actual sim card activating would not work. Ultimately, I had to put the SiM in a different phone, let it activate, and then swap it back to the fold. I even tried eSIM and those didn't work either.
I also noticed that I cannot setup a sim card pin lock. It asks for my current pin. PUK codes from the provider don't work.
Not sure if this is a graphene issue, just posting here for info.