Is it possible to use @import in a header file?

There is a long thread discussing this issue. It's any case where Swift Package symbols, written in Swift, are added to an Objective-C header, and that header is exposed to Swift.

There is a workaround when an Xcode project is also involved using module maps mentioned in the thread. I don't know of a solution though when there are 3 Swift Package targets like you mentioned. I get the same errors.