Display of usage start. What is triggered by this?

They don't because it's too inconvenient to leave the warm office. So, all good.

They were here with us. Checked if the execution matches the plans and if certain regulations were followed (e.g., parapet heights/fall protections or smoke detectors).

They wanted a certificate from the chimney sweep confirming that the heating system has been approved, as well as photos as proof that a part of the floor slab built by the previous owner without permission was demolished as agreed. In principle, they could probably also come for an inspection, but they did not do so. This has nothing to do with property tax, sewage, garbage, or the like. The responsible authorities will contact separately.