On my iphone 11 pro I do not have the automatic brightness problem, and the wifi calls are not deactivated at any time. in my case, if they tell me that it is beta RC, I could perfectly believe it.
Anyway, the automatic brightness if you touch it in the control center, it has been half deactivated as always. because at least when I have had to upload it, it has continued to work, but taking the value I set as a minimum brightness. that is, if I need 25% brightness, but the phone considers that I only need 20%, I manually go up to 25%, from that moment it goes from that 25% to 100%. it never drops to 0%, it always stays at 25%, or whatever you have set. To return to normal, activating and deactivating the automatic brightness is solved. I have had that behavior in ios 12, 13, 14 and now with 15.