Just received an excellent email outlining all that one needs to know about getting my recent purchase of Xiaomi Redmi 12 5G setup for VoLTE. I had worked it out earlier but I followed the guide for mine and my wife's redmi 10 5G.

They also said Xiaomi was going to send an update to these phones to set them up automatically. 

Well done, PB Tech, especially as Xiaomi is not on the 2D list of OK phones.