Example of dynamically populated choices for ACF select field

php

add_filter( 'acf/load_field', 'my_plugin_get_proper_form_templates', 10, 1 );
function my_plugin_get_proper_form_templates($field) {
    if ( 'select_form_tmpl' === $field['name'] ) {
        $forms_cfg = my_plugin_get_form_fields_cfg(); // external function, we get data from here
        $choices = [];

        if (array_keys($forms_cfg)) {
            foreach (array_keys($forms_cfg) as $tmpl_name) {
                $choices[$tmpl_name] = $forms_cfg[$tmpl_name]['label'];
            }
        }

        $field['choices'] = $choices;
    }

    return $field;
}