use proper name

mkosi.extra/calamares/desktop/modules/mount.conf

@@ -11,7 +11,7 @@
 ---
 btrfsSubvolumes:
     - mountPoint: /
-      subvolume: /@systemdOS
+      subvolume: /@kdeos
     - mountPoint: /home
       subvolume: /@home
 

mkosi.extra/usr/bin/_calamares@subvol

@@ -15,10 +15,10 @@ device=$(findmnt --noheadings --nofsroot --output SOURCE "$ROOT")
 mount -o subvol=/ "$device" "$ROOT/system"
 cd "$ROOT/system"
 
+. /etc/os-release
+
 # FIXME set actual version
-mv @systemdOS @systemdOS_0
-ln -s @systemdOS_0 @systemdOS
-btrfs subvolume set-default @systemdOS
+mv @kdeos "@kdeos_$IMAGE_VERSION"
 
 # @home gets created by calamares' mount module
 btrfs subvolume create @snap