After the cell search is complete, a 5G UE automatically selects a PLMN based on...

According to the 3GPP TS 24.008 V15.2.0 (https://www.3gpp.org/DynaReport/24008.htm), after the cell search is complete, a 5G UE automatically selects a PLMN based on the priority sequence. The UE will preferentially select U-PLMN (User Preferred PLMN) for registration. U-PLMN is the PLMN that the user has selected manually or that the user has previously registered with, and it has the highest priority. If U-PLMN is not available, the UE will select RPLMN (Registered PLMN), which is the last registered PLMN. If RPLMN is not available, the UE will select HPLMN (Home PLMN), which is the PLMN that is permanently stored in the UE. Finally, if HPLMN is not available, the UE will select EHPLMN (Equivalent HPLMN), which is the PLMN with the same MCC and MNC as HPLMN.