I’ve been running the iOS 18 RC build for a week or so on my iPhone 15 Pro and had no carrier updates during that time, but this evening after the final release, I was prompted to install a carrier update (O2 59.1) and now have the 5G Standalone toggle in my mobile data settings on my O2 SIM.
The option is greyed out though, claiming “Your current SIM does not support 5G Standalone”, which is curious as it is an eSIM. Must be an account-level thing.
My iPad, on Three, has had no carrier updates yet and is still on Three 59.0.