So far only a few people have recieved the One UI 2.1 update. Depending in the region in the US they live in, Carrier, and if they have an unlocked or carrier locked phone.
I'm still waiting for my unlocked Note 10+ to recieve the update on AT&T. For now, we just have to wait till the update is pushed out to our devices.
I thought most Note 10 customers had already gotten it? So, I would contact AT&T and ask them when they are getting it because I unfortunately have Sprint, and I received the update 2 months ago.