I am using an iPhone 13 Pro Max and have connected to the RS2 via bluetooth - it shows up as connected in my phone’s settings and I am able to use Flow to see the device and menus in the app.
I have managed to connect with Field Maps using an Android device - in the app the RS2 shows up under the provider menu. It is absent from the provider menu on the iPhone, the only option is Integrated.
The posts I have seen state that Bluetooth connectivity is not possible on iOS, though my understanding is that it became an option fairly recently. I’m hoping there’s something I’m missing as this would make the RS2 the receiver of choice among our staff. There is some documentation re: connecting via TCP to use ArcGIS Survey123, but the apps are different enough it doesn’t seem like this is an option with Field Maps.