Systems and methods to support coexistence of multi-connectivity functions in 3GPP network and non-3GPP networks for UEs and to provide traffic routing policies and coordinate with ATSSS operation in 5GS are described. The AF subscribes to a registration-state notification event. A report is sent to the AF from the PCF or NEF. The report indicates a current registration state of a UE and is triggered when the registration state of the UE changes. The report may be sent with or without PDU session information, the former of which may be based on a determination by the AMF or the SMF. Traffic steering is enforced by the MAMS among multiple IP sessions coordinated via a single or a multiple PDU sessions in the 3GPP network.