Forge, Fabric, Neoforge version of datapack: https://www.curseforge.com/minecraft/mc-mods/adventure-dungeons-mod-edition

  Adventure Dungeons is datapack that adds new structures to your Minecraft world. Every structure has a different idea behind it, but it's still trying to look like they're from vanilla Minecraft.

Here's a list of all structures from this datapack:

Cold Lair

Underground dungeon that can be found deeper under overworld's snow biomes. Consist of big room with bridges in middle that connects to other rooms in this dungeon. 

Trial Rooms

Underground dungeon that consists of rooms filled with trial spawners and vaults to loot. Can be found in overworld. 

Bygone Dungeon

Underground dungeon that can be found under forest and plains biomes. Has chests and vaults to loot with trial spawners to fight.

Ruins

Small overworld structure that hidden in gravel or sands. While digging in it you can brush some gravel or sand with your brush to find some loot or even find chest that will have a explorer map to all underground dungeons from this datapack. Has a alternative variant called 'Underground Camp'.

Murky Dungeon

Underground dungeon that can be found under swamps. Labyrinth-like structure, in which will be easy to get lost and has chests and vaults to loot with trial spawners to fight.

Custom advancements

Also this datapack has a custom advancements that will even reward you for finding all structures from this datapack: