Thanks a lot for this! I'm using a Google Pixel 6a and my mobile network carrier is Jazztel (Spain). VoLTE was working fine till some weeks ago but it suddenly stopped working. VoWiFi kept on working fine, by the way.
With this new version a toggle is there to activate VoLTE and it works...but only for outgoing calls in my case; as soon as somebody calls me, the phone goes back to 3G.
Is this something that can be solved by GrapheneOS? Or is it related to my network carrier?