You can display Popup by scrolling at the end using the Post Grid Combo plugin. This article will help you to display a popup by scroll at the end.
To begin, insert a “Popup” block.
Click on the Visibility Tab and click on the Add Group button.
Then Click on the Add Condition Button to add a condition to load the Popup by scrolling at the end.
Here, Choose Scroll End to make the popup display by scrolling to the end.