- The `miller` package has been upgraded from 5.10.3 to [6.2.0](https://github.com/johnkerl/miller/releases/tag/v6.2.0). See [What's new in Miller 6](https://miller.readthedocs.io/en/latest/new-in-miller-6).

- MultiMC has been replaced with the fork PrismLauncher due to upstream
  developers being hostile to 3rd party package maintainers. PrismLauncher
  removes all MultiMC branding and is aimed at providing proper 3rd party
  packages like the one contained in Nixpkgs. This change affects the data
  folder where game instances and other save and configuration files are stored.
  Users with existing installations should rename `~/.local/share/multimc` to
  `~/.local/share/PrismLauncher`. The main config file's path has also moved
  from `~/.local/share/multimc/multimc.cfg` to
  `~/.local/share/PrismLauncher/prismlauncher.cfg`.

- `systemd-nspawn@.service` settings have been reverted to the default systemd behaviour. User namespaces are now activated by default. If you want to keep running nspawn containers without user namespaces you need to set `systemd.nspawn.<name>.execConfig.PrivateUsers = false`

- `systemd-shutdown` is now properly linked on shutdown to unmount all filesystems and device mapper devices cleanly. This can be disabled using `systemd.shutdownRamfs.enable`.

- The Tor SOCKS proxy is now actually disabled if `services.tor.client.enable` is set to `false` (the default). If you are using this functionality but didn't change the setting or set it to `false`, you now need to set it to `true`.

- `services.github-runner` has been hardened.  Notably address families and
  system calls have been restricted, which may adversely affect some kinds of
  testing, e.g. using `AF_BLUETOOTH` to test bluetooth devices.

- The terraform 0.12 compatibility has been removed and the `terraform.withPlugins` and `terraform-providers.mkProvider` implementations simplified. Providers now need to be stored under
`$out/libexec/terraform-providers/<registry>/<owner>/<name>/<version>/<os>_<arch>/terraform-provider-<name>_v<version>` (which mkProvider does).

  This breaks back-compat so it's not possible to mix-and-match with previous versions of nixpkgs. In exchange, it now becomes possible to use the providers from [nixpkgs-terraform-providers-bin](https://github.com/numtide/nixpkgs-terraform-providers-bin) directly.

- The `dendrite` package has been upgraded from 0.5.1 to
  [0.6.5](https://github.com/matrix-org/dendrite/releases/tag/v0.6.5). Instances
  configured with split sqlite databases, which has been the default
  in NixOS, require merging of the federation sender and signing key
  databases. See upstream [release
  notes](https://github.com/matrix-org/dendrite/releases/tag/v0.6.0)
  on version 0.6.0 for details on database changes.

- The existing `pkgs.opentelemetry-collector` has been moved to
  `pkgs.opentelemetry-collector-contrib` to match the actual source being the
  "contrib" edition. `pkgs.opentelemetry-collector` is now the actual core
  release of opentelemetry-collector. If you use the community contributions
  you should change the package you refer to. If you don't need them update your
  commands from `otelcontribcol` to `otelcorecol` and enjoy a 7x smaller binary.

- `services.zookeeper` has a new option `jre` for specifying the JRE to start
  zookeeper with. It defaults to the JRE that `pkgs.zookeeper` was wrapped with,
  instead of `pkgs.jre`. This changes the JRE to `pkgs.jdk11_headless` by default.

- `pkgs.pgadmin` now refers to `pkgs.pgadmin4`. `pgadmin3` has been removed.

- `pkgs.minetestclient_4` and `pkgs.minetestserver_4` have been removed, as the last 4.x release was in 2018. `pkgs.minetestclient` (equivalent to `pkgs.minetest` ) and `pkgs.minetestserver` can be used instead.

- `pkgs.noto-fonts-cjk` is now deprecated in favor of `pkgs.noto-fonts-cjk-sans`
  and `pkgs.noto-fonts-cjk-serif` because they each have different release
  schedules. To maintain compatibility with prior releases of Nixpkgs,