Hi cleardotgames,
I understand your confusion about the different packaging formats.
The Minifantasy assets on Itch.io are distributed as standard graphical assets (PNG files), which is actually the original and primary format for the collection. While these can absolutely be used with any game engine including Unity, they will require manual integration.
To use them in Unity:
- Import the PNG files into your Unity project's Assets folder
- Set the appropriate settings depending on your project setup
- Create your own prefabs or game objects using these sprites
The Unity Asset Store versions were a separate initiative where I packaged everything specifically for Unity with prefabs and ready-to-use components. I think the Unity packs are incredibly handy and well made. Unfortunately, the limited demand on the Asset Store and the resources required to maintain both versions forced me to discontinue Unity releases long time ago (that's why there are only 9 asset packs available in the Asset Store).