@Mafalda61
I think that smart locks which are only activated by an app installed on the device of the person who wants to use them, are a good solution in terms of security.
For example, because there are no physical devices such as number pads that can be seen from the outside. Also, these systems usually come with some sort of configuration that you can set to increase security.
A disadvantage of these systems is that they can be unintuitive to use, so you need to make sure you give instructions well in advance.