It will depend on the PAM solution and what you want to protect with it. For example I did some work with Osirium PAM, and they support the Veeam administrator console natively without any integrations being done on the Veeam side (They use credential injection and JIT Elevation).
If you wanted Veeam to query the PAM each time it needed to authenticate to something (rather than storing credentials using the Credential Manager), that would probably need to be a feature request as I don't believe Veeam can do this at the moment.
If you are looking to better protect the encryption keys for your backups, if you have a Key Management Server that implements KMIP you can
use Veeam with that. This isn't really a PAM, but does achieve something similar in that it it is able to get the private key for encrypted backups off the Veeam server onto your KMIP server and presumably stored somewhere safe like an HSM.