The skyshard inside the dungeon has had its location changed due to post-launch remodeling. It’s the same with all the shards within the Stonefalls solo dungeons. When you enter the Inner Sea Armature, keep to your right. The shard is in the corner of the northernmost room.
Inner Sea Armature Entrance.
Public dungeon Map Location.
In the corner of the room.
Sand Kingdom Moons - Super Mario Odyssey Power Moons