1.21.10 was already supported and no changes were needed.
Fixed
Fixed an error caused by skulls when opening GUIs in older server versions (~1.21.7 below)
Fixed an error caused by the previous build when spawning holograms.
Fixed some command permission issues caused by the previous version.
Fixed the placeholder context when opening someone else's nexus.
You can no longer ride horses in protected territory unless you are the owner that tamed it.
Fixed some duplicated messages when interacting in enemy territory.
You can now hit passive mobs that can turn hostile after being chased in an enemy's territory. For example if you get chased by a wolf that's attacking you, you can attack it anywhere.
Others
Kingdoms chest inventory logger will now wait 10 seconds before bulking changes.
The plugin now uses a mirror for downloading libraries. Which is basically more ethical without going into details.
/k gui is now blocked by default for normal players.