A wireless device is configured for wirelessly communicating with one or more types of Radio Access Networks (RANs) providing control-plane connectivity to one or both of a first type of core network and a second type of core network. The device configures a Packet Data Convergence Protocol (PDCP) at the device, e.g., at least for initial control-plane signaling, in dependence on whether the device is connected, or connecting, to the first type or the second type of core network. In at least one embodiment, the device configures PDCP for the second type of core network as a default choice, when control-plane connectivity to the second core network is available. In an example arrangement, the RAN types are LTE and 5G New Radio (NR), and the core network types are Evolved Packet Core (EPC) and 5G New Generation Core Network (NGCN).