Trying to duplicate a PDB from a backup of a CDB into an existing CDB.

Oracle Enterprise Edition 19c on Exadata Gen2, All DBs are encrypted (TDE). The Source CDB and Dest CDB do not have access to one another, so I'm doing a backup to an NFS share.

Both DBs use TDE, and the passwords are different.

Documentation says to duplicate the pdb to an aux_CDB, but you have to be able to open the keystore of the aux_CDB and import the encryption key from the source CDB. However, the document also says duplicate pdb into an existing CDB from RMAN backup is not supported.

How do I import the encryption key without the CDB already existing, and how do I duplicate the PDB if duplication from rman backup is not supported? Am I over thinking this or am I missing a step?