I'd have to recommend staying away from Carthage. We went the Carthage route on one project due to many of the issue mentioned here in regard to CocoaPods.

Only to eventually rip it out and revert the project back to CocoaPods as Carthage has it's own share of issues and in fact suffers from many of the same problems as CocoaPods.

We'd like to use SPM, but our app has too much reliance on some third-party libraries that we simply must use. And those libraries are currently only provided as pods. Even large companies (Google) have yet to fully support SPM in their developer-provided tools.