Hi @maxaud
If you want to do it for a select field, you can try to follow this guide: https://www.advancedcustomfields.com/resources/dynamically-populate-a-select-fields-choices/.
But in general, you should be able to modify the returned fields by using the acf/load_field and modify the returned value by using the acf/load_value filters.
I hope this helps 🙂
