OOS11のrootedでのVolte化って、これ？
https://forum.xda-developers.com/oneplus-8-pro/help/help-pdc-recognizing-phone-android-11-t4166849/amp/?__twitter_impression=true

なかなか面倒なのね。
https://docs.google.com/document/d/1ejLtVQTpXZaB5XGNOBRI5dZV4GpuCKtHOGo6v49hWdY/edit?usp=sharing