By default NetworkManager stores profiles in the keyfile format on RHEL9; in alternative, the old ifcfg format is still supported and will be used if the user manually sets 'plugins=ifcfg-rh' in the configuration and then creates a new profile. The ifcfg settings plugin is now deprecated upstream [1]; this means that new properties will not be supported for profiles stored in ifcfg format. To inform users about the change, we are going to: 1. update the documentation (man pages, etc.) to state that ifcfg is deprecated 2. log a message at startup when a profile is found in ifcfg format 3. report an error when updating a profile in ifcfg format and there are unsupported properties. At the moment the only unsupported properties are 'link.*' 4. add an entry to release notes [1] https://lists.freedesktop.org/archives/networkmanager/2023-May/000103.html