PSAkeepInventory not working? Every renamed gamerule in Java 1.21.11+ (old vs new names)

Since Java 1.21.11 the gamerules have new names in snake_case, and some were renamed completely. If /gamerule keepInventory true suddenly says "unknown", this is why. Bedrock still uses the old names.

Old name → new name (Java)

The full IDs carry a namespace (for example minecraft:keep_inventory), but typing the short name works in the command.

Copy-paste examples

/gamerule keep_inventory true
/gamerule advance_time false
/gamerule spawn_phantoms false
/gamerule players_sleeping_percentage 50

On Bedrock it is still /gamerule keepinventory true.

For server owners

Plugins, datapacks and command blocks that set gamerules by the old name will fail quietly. Search your configs and functions for the old names after updating, and update plugins that change gamerules.