setup rDNS when using whn/cpanel?

I Hope everyone is doing well.

Having difficulty getting reverse dns to show my hostname name.domain.org

Asked Linode support and for a pretty fundamental part of running this system, they said to ask here. Surprised they didn't have the slightest hint on what to do. Maybe time to move on to elsewhere, I dunno.

In any event, the domains are running in whm/cpanel and linode is my bare metal. When I run "host xx.xx.xxx.xxx" from command line it still returns the domain name and not the hostname which should be hostname.domain.org.

whm/cpanel tech support says this needs to be resolved on the bare metal, not with them.

I have set the rDNS in the network tab to hostname.domain.org but it's not propograing.

Any help very much appreciated.