I noticed that VoLTE option is not available in the Connection Settings on Galaxy S21 Ultra on One UI Beta 2. I swtiched SIM and inserted it into Note 20 Ultra and VoLTE works just fine. Both phones are factory unlocked.
I agree that it might be a carrier specific setting but I am using the same SIM on 2 different phones. On Note 20 Ultra VoLTE it is enabled automatically while on S21 Ultra it does not and there is no option to enable it either. Carrier is irrelavant.
Every Carrier revisits and update their requirement every few months and we implement them on our devices following descending order of release of device itself. Even though option is currently available on Note 20 ultra, once Android 12 update is released for Note 12, option may not be available.
