The ArchivedContent is currently set as private in its tags but it shouldn't. It is to the final (or intermediate) content type to decide if it is a private content type.
Because of this, some content types are no more searchable by default.

I checked all the current kernel and plugins content types which inherit ArchivedContent, but they have their own tags so it is OK for these. But on specific content types, it is not always like this.