For me the dealbreaker on Graphene was inability to record my phone conversations. I went back to Lineage.
GrapheneOS can record phone calls just fine, there is a record button in the dialer.
I can confirm this, and will add: on my Pixel 6 running GrapheneOS, I have to scroll down the "6 pack" of buttons on the in-call screen to reveal the record call button. There is no UI hint that these buttons are within a scrollable element, so discoverability is poor.
i too would like to know, I use graphene right now and can't imagine it being better.