Is there a way to have a app add users to a list that then have access to the same data?
Yes. First, make sure there is a relationship between users and the collection you want to add the users to.
Then, create a list of Users with a filter where relationship list item = empty.
Add a countdown timer inside the list. Create a list from this countdown timer of the list collection you wish to add.
So you’ll have a list of users that contains a list of the other collection that contains a countdown timer.
Set the timer to 1 second. Set the timer finished action to update current collection > add current user.