If mice are your big concern, then check out this type of feeder. We bought one of these for that reason.
Top picture shows feeder closed. The bottom shows it open. It has a flat area the chickens must stand on in order for the door to open. But when it's closed it forms a nice tight rat proof container.
It's all metal too.
I didn't buy this exact brand but the design is exactly the same as I bought.
More info here....
https://www.raising-happy-chickens.com/best-automatic-chicken-feeder.html

Top picture shows feeder closed. The bottom shows it open. It has a flat area the chickens must stand on in order for the door to open. But when it's closed it forms a nice tight rat proof container.
It's all metal too.
I didn't buy this exact brand but the design is exactly the same as I bought.
More info here....
https://www.raising-happy-chickens.com/best-automatic-chicken-feeder.html