In a new document-based UIKit app, specifying in the Info.plist an import type identifier of public.log that conforms to public.content, public.data, public.item accomplishes this.
In a new document-based SwiftUI multi-platform app, doing the same crashed at the DocumentGroup initializer with the error
_SwiftData_SwiftUI/Documents.swift:91: Fatal error: The document type is public.log which does not conform to com.apple.package.
This initializer expects the document type to be a package.