At WWDC 2019/iOS 13, Apple added support for legacy Bluetooth 2.0 devices to CoreBluetooth.
Some existing Bluetooth 2.0 devices implement RFCOMM, however CoreBluetooth itself lacks an RFCOMM API. What CoreBluetooth does offer is an L2CAP API.
Since RFCOMM is normally implemented on top of L2CAP, in terms of the Bluetooth protocol stack, is it therefore viable to implement RFCOMM on iOS?
As an aside, currently I am unable to get iOS to discover an advertising Bluetooth 2.0 peripheral which implements an RFCOMM interface. So there are additional technical challenges to be overcome as well.