- [services.xserver.videoDrivers](options.html#opt-services.xserver.videoDrivers) no longer uses the deprecated `cirrus` and `vesa` device dependent X drivers by default. It also enables both `amdgpu` and `nouveau` drivers by default now.

- The `kindlegen` package is gone, because it is no longer supported or hosted by Amazon. Sadly, its replacement, Kindle Previewer, has no Linux support. However, there are other ways to generate MOBI files. See [the discussion](https://github.com/NixOS/nixpkgs/issues/96439) for more info.

- The apacheKafka packages are now built with version-matched JREs. Versions 2.6 and above, the ones that recommend it, use jdk11, while versions below remain on jdk8. The NixOS service has been adjusted to start the service using the same version as the package, adjustable with the new [services.apache-kafka.jre](options.html#opt-services.apache-kafka.jre) option. Furthermore, the default list of [services.apache-kafka.jvmOptions](options.html#opt-services.apache-kafka.jvmOptions) have been removed. You should set your own according to the [upstream documentation](https://kafka.apache.org/documentation/#java) for your Kafka version.

- The kodi package has been modified to allow concise addon management. Consider the following configuration from previous releases of NixOS to install kodi, including the kodiPackages.inputstream-adaptive and kodiPackages.vfs-sftp addons:

  ```nix
  {
    environment.systemPackages = [
      pkgs.kodi
    ];

    nixpkgs.config.kodi = {
      enableInputStreamAdaptive = true;
      enableVFSSFTP = true;
    };
  }
  ```

  All Kodi `config` flags have been removed, and as a result the above configuration should now be written as:

  ```nix
  {
    environment.systemPackages = [
      (pkgs.kodi.withPackages (p: with p; [
        inputstream-adaptive
        vfs-sftp
      ]))
    ];
  }
  ```

- `environment.defaultPackages` now includes the nano package. If pkgs.nano is not added to the list, make sure another editor is installed and the `EDITOR` environment variable is set to it. Environment variables can be set using `environment.variables`.

- `services.minio.dataDir` changed type to a list of paths, required for specifying multiple data directories for using with erasure coding. Currently, the service doesn't enforce nor checks the correct number of paths to correspond to minio requirements.

- All CUDA toolkit versions prior to CUDA 10 have been removed.

- The kbdKeymaps package was removed since dvp and neo are now included in kbd. If you want to use the Programmer Dvorak Keyboard Layout, you have to use `dvorak-programmer` in `console.keyMap` now instead of `dvp`. In `services.xserver.xkbVariant` it's still `dvp`.

- The babeld service is now being run as an unprivileged user. To achieve that the module configures `skip-kernel-setup true` and takes care of setting forwarding and rp_filter sysctls by itself as well as for each interface in `services.babeld.interfaces`.

- The `services.zigbee2mqtt.config` option has been renamed to `services.zigbee2mqtt.settings` and now follows [RFC 0042](https://github.com/NixOS/rfcs/blob/master/rfcs/0042-config-option.md).

 The yadm dotfile manager has been updated from 2.x to 3.x, which has new (XDG) default locations for some data/state files. Most yadm commands will fail and print a legacy path warning (which describes how to upgrade/migrate your repository). If you have scripts, daemons, scheduled jobs, shell profiles, etc. that invoke yadm, expect them to fail or misbehave until you perform this migration and prepare accordingly.

- Instead of determining `services.radicale.package` automatically based on `system.stateVersion`, the latest version is always used because old versions are not officially supported.

  Furthermore, Radicale's systemd unit was hardened which might break some deployments. In particular, a non-default `filesystem_folder` has to be added to `systemd.services.radicale.serviceConfig.ReadWritePaths` if the deprecated `services.radicale.config` is used.