I’ve got a custom post type where I want it to generate a url with a hash as a get parameter, so I have a custom field which the name of ‘url’ but I want to be able to set that value of it automatically when the user published the custom post. Is this possible?
Use an acf/save_post filter https://www.advancedcustomfields.com/resources/acf-save_post/. In this filter you can get other values from the post and use update_field() to set other values https://www.advancedcustomfields.com/resources/update_field/.