you’re right, acf/pre_save_post only runs on the front end.
There are lots of WP hooks for this, but I’ve done tests and none covers all possibilities.
Oddly enough, the only one that works really well is
add_filter(‘post_updated_messages’,’ my_function’);
This is triggered “always”, except in delete post, that have to use
add_action(‘delete_post’, ‘codex_sync’, 10);
I do not know if there is a better option
Thanks for your help