Wifi calling is a carrier service. Often carriers don't enable it on unlocked phones.
I use AT&T and I don't see Wifi calling on my Note 20 Ultra. But people have reported that the Beta software being rolled out does enable it.
The beta should make no difference as the carrier feature is simply not enabled on your AT&T account, and it won't be until their system identifies an AT&T version of the device.
This might be, but once the carrier version comes out, it will lock it down again. If you are on a AT&T LOCKED device, then you have WiFi calling. I am on AT&T and have a Note20 Ultra, and do indeed have this feature. (right between WiFi and Bluetoots on the screen in the OP's Screenshot) I would not get used to it if the Beta enabels it for you...