Q:

AppStore: How to publish more apps in a single app container?

In order to comply AppStore Review Guidelines, I can't publish multiple similar apps so I need to combine apps with a common features set into a single "container" app. 
I've googled a lot, but I can't find a way to do something like https://apps.apple.com/it/developer/intemodino-group-s-r-o/id557849644
I've heard to use In-App Purchase API to deliver different content, but I'm making free apps.
I'm newbie here, so I'm sorry for possible misunderstandings.

A:

The link you posted is showing how to create "app bundles" -- so, for that example, the publisher sells multiple apps in a bundle for a lower price than buying all the apps individually. 
What you're dealing with sounds different... 
For example, suppose you have a "Pretty Pictures of Trees" app, a "Pretty Pictures of Flowers" app, a "Pretty Pictures of Rivers" app, etc.
Apple wants you to take your basic "show the pictures" structure and implement something like IAP to allow users to download the different "categories" of pictures.
And. IAP can be free.

Edit
To elaborate a little...
With the above example, you might display a table of "Categories" - or maybe a grid if "Category Icons."
When the user selects a category, check if that "option" has been purchased - again, IAP pricing can be set to Free.
If it has not, present the user with a "Download this Category content" interface, and use the IAP api to purchase / download the content.
If it has already been "purchased," branch into your image viewing controller, passing the category name / ID (however you're tracking it), and display those images.

