-`light` has been removed because it was unmaintained.
`brightnessctl` and `acpilight` provide similar functionality.
-`opensmtpd-filter-dkimsign` is now installed into `libexec/smtpd` instead of `libexec/opensmtpd` so that now it is properly linked into the environment built by `services.opensmtpd.procPackages`. If you hardcoded path to `filter-dkimsign` please consider using this option.
-`services.openssh.settings.AcceptEnv` now explicitly defined as an option that takes a list of strings, to facilitate option merging. Setting it to a string value is no longer supported.
- All Xfce packages have been moved to top level (e.g. if you previously added `pkgs.xfce.xfce4-whiskermenu-plugin` to `environment.systemPackages`, you will need to change it to `pkgs.xfce4-whiskermenu-plugin`). The `xfce` scope will be removed in NixOS 26.11.
