No, there isn’t any way to alter the way this type of field is displayed. If you want a checkbox field then you’ll need to create a checkbox field. That would mean that you’d need to do a lot more work getting the related posts though.
Welcome to the Advanced Custom Fields community forum.
Browse through ideas, snippets of code, questions and answers between fellow ACF users
ACF wouldn’t be so widely used in WordPress if it didn’t have some pretty amazing capabilities. In this article, we look at a few of the features we’ll discuss during “7 things you didn’t know you could do with ACF” at #WPEDecode later this month. https://t.co/5lnsTxp81jpic.twitter.com/Yf0ThPG1QG