I’m not sure which versions of SwiftPM can successfully have an Objective C target import a Swift target. It wasn’t possible with the initial Objective C support, but then support was added. After that some bugs popped up, but they were then fixed. However, that is all with respect to the master branch and I don’t know how any of that timeline corresponds to actual releases. It could even be that nothing released so far can do it.
Here is one related thread, but if you search, you’ll find more: