I don't know if it's in upstream, but for a few days I've been using my phone (GrapheneOS) as a "Wi-Fi only" phone. Radio is turned off (Airplane mode and toggling Wifi does leave the radio off).
Since I'm only using Signal nowadays and I surely don't expect phone calls, it makes sense to turn on radio only when I need it.
Just a single-user instance, nothing fancy here. I won't bite, I promise.