Am I allowed to install something myself in the fusebox?

Connecting in the meter cabinet is work for a registered installer

No, hanging the box itself and connecting it in the meter cabinet is not something a landlord or a random handyperson does themselves. The meter cabinet is part of the electrical installation of a property, and work on it falls under the rules that apply to low-voltage installations. This means that the physical installation and connection of a module in the meter cabinet is in practice done by a registered installer or electrician, not by the owner of the property or the operator of the rental.

What does fall to the landlord is ordering the module and activating it afterwards. That activation happens via a phone and Bluetooth, without needing to work on the wiring, so that part falls outside the installation work that requires a professional. The division is therefore: mounting and connecting is work for the electrician, the rest of the setup the landlord can do themselves.

Where this requirement comes from

This division follows from NEN 1010, the standard for low-voltage installations, which has acquired legal status via the Building Decree for electrical installations in buildings. Because the standard sets requirements for how installations are laid out, expanded and connected, adding a device in the meter cabinet falls under those requirements as soon as it involves a connection to the existing groups. The standard itself does not describe who exactly may perform the action, but the requirements for correct and safe execution mean that in practice this is done by someone with the appropriate technical knowledge. For the exact requirements for execution, the full standard is the source to consult.