I relationship field cannot be used to select terms in a category.
A page link field will allow selecting posts and archive pages. This is the closest that you will be able to get using a built in ACF field.
To allow multiple selections of different type of fields the solution is to use a repeater with multiple sub fields
- Link Type – Radio or Select field to select “Post/Page”, “Category”, etc..
- Post object fields conditional if “post/page” selected
- Category Taxonomy field conditional if “category” is selected
- etc…
