nixos/doc/manual: add upgrade notice to release notes

nixos/doc/manual/release-notes/rl-2605.section.md

@@ -185,6 +185,13 @@ See <https://github.com/NixOS/nixpkgs/issues/481673>.
 
 - `services.caddy` now supports setting `httpPort` and `httpsPort` and opening them in the firewall via `openFirewall`.
 
+- The latest available version of Nextcloud is v33 (available as `pkgs.nextcloud33`). The installation logic is as follows:
+  - If [`services.nextcloud.package`](#opt-services.nextcloud.package) is specified explicitly, this package will be installed (**recommended**)
+  - If [`system.stateVersion`](#opt-system.stateVersion) is >=26.05, `pkgs.nextcloud33` will be installed by default.
+  - If [`system.stateVersion`](#opt-system.stateVersion) is >=25.11, `pkgs.nextcloud32` will be installed by default.
+  - `nextcloud31` is EOL and was thus removed.
+  - Please note that an upgrade from v31 (or older) to v33 directly is not possible. Please upgrade to `nextcloud32` (or earlier) first. Nextcloud prohibits skipping major versions while upgrading. You can upgrade by declaring [`services.nextcloud.package = pkgs.nextcloud32;`](#opt-services.nextcloud.package).
+
 - `services.slurm` now supports slurmrestd usage through the `services.slurm.rest` NixOS options.
 
 - `services.kanidm` options for server, client and unix were moved under dedicated namespaces.

nixos/modules/services/web-apps/nextcloud.md

@@ -5,7 +5,7 @@ self-hostable cloud platform. The server setup can be automated using
 [services.nextcloud](#opt-services.nextcloud.enable). A
 desktop client is packaged at `pkgs.nextcloud-client`.
 
-The current default by NixOS is `nextcloud32` which is also the latest
+The current default by NixOS is `nextcloud33` which is also the latest
 major version available.
 
 ## Basic usage {#module-services-nextcloud-basic-usage}