If you are talking about SgNB HO, then it is not allowed in NSA. There is only SgNB change. However MeNB can do intra-site HO the usual way keeping the SgNB intact (update context only). In case of inter MeNB HO, SgNB must be released before the HO.
In case of LTE out of service can UE serviced by NR alone in Non stand alone architecture ?