Apparently, all of the cm device commands have been disabled as of v14.1.2.3 (and MV command was already depricated). Changing hostname does not change the device name since v13.1 even if the device is not in a DSC cluster. However, the Ansible bigip_hostname module attempts to change the device name when changing hostname, though this is not documented. It will fail if the device is already in a trust relationship.
Even when the device isn't (and never has been) in a device trust relationship, as when a new vCMP guest is created, I've not been able to change the name via TMSH - it always says that the device is referenced by /Common/device_trust_group; actually, that is not found, but it's referenced in trust-domain Root, which cannot be deleted.
I always have to do it via the ConfigUI.