I have discussed with Veeam support and apparently there is no way to use only Kerberos authentication with Veeam. Therefore, if you're planning to have a NTLM free environment, Veeam would be out of the equation. The following services do not seem to work in Kerberos:
1) File indexing
2) File restoration
I'm starting this thread to request for the feature to be in the next release of Veeam B&R. It is high time for Veeam to catch up with the latest Enterprise security standards.