Displaying Regular WordPress Custom Fields with ACF 5.6.0+
If you’re an ACF user, you may have noticed in the latest updates of the plugin that the regular WordPress custom fields interface is no longer showing on Edit screens. This was done largely for speed boosting reasons and you can read more about the reasoning here. Starting in version 5.6.0 of the plugin, it is default behavior for custom fields to no longer be shown with ACF in play.
If there is a scenario where you need to work with both ACF and regular custom fields, you can simply drop this filter into your theme’s functions.php file to override default behavior here.