This plugin is an add-on for Advanced Custom Fields. It allows you to use “post_mime_type” filter in “relationship” field.
If this plugin helps you, please give it a good rating. If you have any problems, please ask me. I’m happy to help.
After you Install & Activate plugin you will see “MIME Type” filter option in acf relationship field.
Here you will see all mime types of attachment post type.
You can select multiple mime types to filter post list in relation ship metabox.