I’ve got a project using both right now (because not everything is available on spm yet). It works fine. There is one issue I’ve come across - SPM and cocoa pods are not aware of each other’s packages / pods.
So if module “abc” and “xyz” both depend on another, module, “efg”, under a single package manager, and “efg” of the matching version requirements will be downloaded. If “abc” is in one package manager, and “xyz” is another, you’ll end up with two copies of “efg” in your app, possibly different version of it too. This could lead to undefined behavior and crashes.
So basically make sure the packages you download between SwiftPM and coacoapods don’t share any dependencies.
It’s pretty easy to add CocoaPods support to a random library, so I would suggest doing that. SPM still doesn’t support things like automatic license rendering that are usually required with OSS libraries.