Vault Signed SSH certificates integrate with PKI(certificates)

According to the document, the Client key signing was implemented.
The step of configuring CA uses vault writes ssh-client-signer/config/ca generate_signing_key=true.
For the final certificate, use ssh-keygen -Lf to view the message information and find that the signing ca in it should be generated by itself.

I want to know how to obtain the Signing CA certificate information?
Vault also has PKI (certificates) function. Can the CA configured here be used as SSH CA? Can the two be integrated?