If you're looking for an eco-friendly case, this GEAR Onsala Eco Friendly case for iPhone 12 Mini is a good choice. 

The surface of this iPhone 12 Mini case is made of FSC eco-friendly paper, which has a slightly rough surface. Even though the case is made of paper, it is still water resistant. It will therefore not be damaged by rain or water drops. The case opens and closes using a flap that can be closed on the back of the case. In this way, the case is completely free of magnets and is made only of biodegradable materials. 

On the inside, there is a bio-degradable back case for the iPhone 12 Mini in which the phone is placed. With this eco-friendly case you not only protect your iPhone but also the planet by reducing plastic waste. On the other side, there are three pockets for credit cards and a large pocket for cash. The inside surface is also made of FSC certified paper.

FSC certificate:

• FSC is the only global labelling scheme for paper and wood, and is strongly supported by organisations such as WWF, Greenpeace and World Forests.
• They help to safeguard the natural and social environment of the forests from which the wood comes.

Note: that the inside case has a matt green color (See picture 4)