Sometimes you need to ensure that a system registered into Satellite has a specific hostname, because the current one is unacceptable for a number of reasons (it might collide with another one, etc).

The Satellite documentations points to the fact that you can override the name by configuring a setting in the subscription-manager facts, however this does not seem to work in newer (6.12+) versions of Red Hat Satellite.

In the latest testing I did, this way ensures the system is registered with the requested hostname in Satellite.

Ensure the old host and content hosts are deleted from Satellite (if required).
Add the requested hostname in /etc/hosts of the system, bound to one of its IPs. It does not matter if it's not the first entry associated to the IP.

Ensure that /etc/rhsm/facts/katello.facts has this settings:

{
"network.fqdn":"new-name.example.com",
"network.hostname":"new-name.example.com",
"network.hostname-override":"new-name.example.com"
}

subscription-manager register --org="ORGANIZATION" --activationkey="ACTIVATIONKEY" --force --name=new-name.example.com

In addition to this, it seems that simply setting the network.hostname-override parameter does not longer work by default. Satellite can be configured to obey this parameter, but the rest of the configuration is still required.

Some relevant documents:

https://access.redhat.com/solutions/3166211 - Registered content host appears with a different hostname in Red Hat Satellite WebUI.
https://access.redhat.com/solutions/3732221 - network.hostname-override is not overriding the hostname of server for registration

Happy hacking!