We don't support including precompiled binaries in Swift packages, yet, except for libraries and frameworks installed on the system. There is a pitch proposal for this feature: [PITCH] Support for binary dependencies - #95 by abertelrud
You can use unsafeFlags to still do it, but this will mean your package is not usable as a transitive dependency, so that's not really suitable for your case where you want to provide a framework.
If "signalProcessingSDK" is a set of libraries you are building with a different build system today, you could look into turning it into a package itself.