improve selecting latest zfs kernel

nix/installer.nix

@@ -4,15 +4,11 @@
   pkgs,
   ...
 }:
-let
-  latestZfsCompatibleLinuxPackages = lib.pipe pkgs.linuxKernel.packages [
-    builtins.attrValues
-    (builtins.filter (kPkgs: (builtins.tryEval kPkgs).success && kPkgs ? kernel && kPkgs.kernel.pname == "linux" && !kPkgs.zfs.meta.broken))
-    (builtins.sort (a: b: (lib.versionOlder a.kernel.version b.kernel.version)))
-    lib.last
-  ];
-in
 {
+  imports = [
+    ./latest-zfs-kernel.nix
+    ./nix-settings.nix
+  ];
   # more descriptive hostname than just "nixos"
   networking.hostName = lib.mkDefault "nixos-installer";
 
@@ -24,7 +20,6 @@ in
 
   # use latest kernel we can support to get more hardware support
   boot.zfs.package = pkgs.zfsUnstable;
-  boot.kernelPackages = latestZfsCompatibleLinuxPackages;
 
   documentation.enable = false;
   documentation.man.man-db.enable = false;
@@ -41,10 +36,6 @@ in
     # alternative to nixos-generate-config
   ] ++ lib.optional (pkgs.lib.versionAtLeast lib.version "24.11") pkgs.nixos-facter;
 
-  imports = [
-    ./nix-settings.nix
-  ];
-
   # Don't add nixpkgs to the image to save space, for our intended use case we don't need it
   system.installer.channel.enable = false;
 }

nix/latest-zfs-kernel.nix

@@ -0,0 +1,26 @@
+{
+  lib,
+  pkgs,
+  config,
+  ...
+}:
+
+let
+  isUnstable = config.boot.zfs.package == pkgs.zfsUnstable;
+  zfsCompatibleKernelPackages = lib.filterAttrs (
+    name: kernelPackages:
+    (builtins.match "linux_[0-9]+_[0-9]+" name) != null
+    && (builtins.tryEval kernelPackages).success
+    && (
+      (!isUnstable && !kernelPackages.zfs.meta.broken)
+      || (isUnstable && !kernelPackages.zfs_unstable.meta.broken)
+    )
+  ) pkgs.linuxKernel.packages;
+  latestKernelPackage = lib.last (
+    lib.sort (a: b: (lib.versionOlder a.kernel.version b.kernel.version)) (builtins.attrValues zfsCompatibleKernelPackages)
+  );
+in
+{
+  # Note this might jump back and worth as kernel get added or removed.
+  boot.kernelPackages = latestKernelPackage;
+}