Thanks @hube2! 🙂
I doubted that, too.
Using `$term_guests = get_term_by(‘name’, ‘Guest’, ‘categories’);
$term_id_guests = $term_guests->term_id;`
solved my problem. I didn’t really follow the part about acf/load_field, but I put the code in functions.php after registering the term and before registering the ACF fields, so I think there is no need (especially since it works).
Of course, I understand, that’s why I said it was meta.