Perfect forward secrecy requires the exchange of ephemeral keys. If you use either ECC or RSA for this and the traffic is captured a quantum computer will break

Perfect forward secrecy requires the exchange of ephemeral keys. If you use either ECC or RSA for this and the traffic is captured a quantum computer will break it. All perfect forward secrecy means is that you delete your own ephemeral private keys, the public keys stay in the record. And a quantum computer will recover the deleted private keys. Also, none of the currently accepted post-quantum cryptographic algorithms offer a Diffie-Hellman construction. They use KEM (Key Encapsulation Mechanism).