Advanced Custom Fields: Location rule for query page by parent parent template. – https://www.advancedcustomfields.com/resources/custom-location-rules/

acf-parent-template-rule.php

<?php 

add_filter('acf/location/rule_types', function($choices) {
	$choices['Page']['parent_template'] = 'Page Parent Template';
	return $choices;
});

add_filter('acf/location/rule_values/parent_template', function($choices) {
	$templates = wp_get_theme()->get_page_templates();
	$choices = array_merge($choices, $templates);

	return $choices;
});

add_filter('acf/location/rule_match/parent_template', function($match, $rule, $options) {
	$pageParent = null;

	if (isset($options['page_parent']) && $options['page_parent']) {
		$pageParent = $options['page_parent'];
		unset($options['page_parent']);
	} elseif (isset($options['post_id']) && $options['post_id']) {
		$post = get_post($options['post_id']);
		$pageParent = $post->post_parent;
	}

	if (!$pageParent || $pageParent <= 0) {
		return false;
	}

	$template = get_page_template_slug($pageParent);

	if ($rule['operator'] == '==') {
		$match = $rule['value'] === $template;
	} elseif ($rule['operator'] == '!=') {
		$match = $rule['value'] !== $template;
	}

	return $match;
}, 10, 3);