It will not be possible to remove the physical domain name entry from Katapult should you have any virtual machines that make use of it as part of the hostname/FQDN, although you can certainly point the nameservers / other DNS elsewhere should you need to. Be mindful that doing so could break access to any virtual machines you may have which use the domain unless you configure associated DNS records elsewhere.
The domain has now been removed from the Katapult system.