Package by feature for APIs that are exporting or / and importing data

Question

We are generally following the package-by-feature approach, which is great.

However, one specific case is constantly causing confusion and inconsistencies, and I'd like to know your approaches in this regard:

Packaging API implementations that import, export or import and export data (by feature)

We have had multiple solutions to structure our classes in packages so far:

1. Having a top-level /api/exports/ and /api/imports/ package followed by <vendor>
2. Having a top-level /api/ package followed by <vendor>/exports/ and <vendor>/imports/
3. Having a top-level /api/ package followed by <vendor> with no specific exports or imports package, but rather a mixture of everything in it
4. Having plain feature packages (no top-level /api/, where the vendor name equals the feature name, containing exports and imports directories
5. Having plain feature packages (no top-level /api/, where the vendor name equals the feature name, containing an /api package

How do you deal with external APIs in your project structure, that either import or export data or do both?