Hello, You have to use XCFrameworks. With the introduction of M1, lipo cannot be used anymore, because it will complain that arm64 simulator and iPhone arm64 are the same thing.

I found a workaround. It seems that XCFramework are not Frameworks, thus they cannot be modularized. So I did copy the C "umbrella" header to my source tree, and defined an explicit module in a custom module.modulemap (adding a custom umbrella header too). I can successfully import this submodule in my swift code, and call C stuff. Here's the modulemap code: framework module Add { umbrella header "Add-umbrella.h" export * module * { export * } explicit module Core { private header "add.h" export * } }