React Native on Apple Silicon M1 – The linked library ‘libPods-ProjectName.a’ is missing one or more architectures required by this target: x86_64

I had the same issue and finally, I fixed it. There are 2 main reasons for the errors:

1. arm64 architecture support & and Xcode 12 compatible version have not been provided by many popular third party libraries yet (like Firebase, AFNetworking, etc). Xcode 11 used to automatically translate building for arm64 for the simulator into building for x86_64, but now that arm64 is a valid simulator architecture (it’s the Apple Silicon architecture), that translation no longer occurs.

2. Because the Valid Architectures build setting has been removed from Xcode 12, the Project file, opened in Xcode 12, will auto-generate a VALID_ARCHS macro in User-Defines, and this macro will make the build fail.

I follow all steps in this post: https://medium.com/@khushwanttanwar/xcode-12-compilation-errors-while-running-with-ios-14-simulators-5731c91326e9

Final step was updating all pods by running below command inside the project folder:

pod deintegrate
pod update

Then I exclude the arm64 for the Simulator architecture, both from main project and the Pod project.

Clean the project (⇧ + ⌘ + k) then run.