Reply To: Can I work with version 2.9 or just start again with 2.8?

In 2.91 you can hide/unhide a Collection from the View Layer by using the checkbox:

This is exactly the same as right-clicking the Collection and under View Layer select Include or Exclude from View Layer:

When you’ve hidden a Collection this way, you can press SHIFT+A > Collection Instance > …   to add an instance of that hidden Collection