Discerning Furnace [Forge]

This is a Forge port of the original Discerning Furnace for Fabric. The creator stated that the mod license is MIT "so anyone else is free to port it"

This is useful for sorting items and for preventing clogs in furnace arrays.
It only prevents automated insertion, e.g. via hoppers and droppers, players may still insert any item.
It affects all vanilla furnaces, and modded furnaces that don't have their own way of limiting inputs should work as well.