KeepLootTable

This simple mod causes the lootable block to not reset the NBT tag of the loot table after generating loot and changes the logic slightly to prevent loot from re-generating.

This mod should work with all types of lootable blocks: Chest, Barrel, Shulker Box, Dropper, etc.

Where can this be useful?

This allows multiple players to get advancements for looting Chests. For example, "War Pigs" for looting a Chest in a Bastion Remnant from Vanilla, or the "I am Loot!" advancement for looting each type of loot Chest from BlazeandCave's. This will eliminate the situation in which a player finds a rare Chest but does not get an advancement for opening it, because another player opened it first before him.

Client/server?

This is a server-side mod; that is, it can work both in your single-player game and on a dedicated server.