"not supported" does not necessarily mean that it does not work.
I read many posts here in the forums, there are some people which can do backups of vSphere 6.5 with Veeam v9.5 or v9 and others cannot.
It is very dependent on the infrastructure you have in your company (or at your customer).
If i'm not wrong there is no graceful way of downgrading from v9.5 to v9. That means you have to uninstall Veeam v9.5 completely and install v9 from scratch.
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