Alternative to central/decentralized ventilation

ohoh, apparently the HB has no idea (about the funding conditions of the BAFA).
Discussing the meaningfulness of this joint regulation with the HB is not goal-fulfilling. It is solely about creating circumstances for the BAFA that lead to the fulfillment of the funding conditions. This can be a BUS (but it would have to be provided in the models that they also "talk" to each other). Via KNX or possibly even a Raspberry PI with some generic actuators or even, according to the report in another forum, a timer switch (which I find quite absurd).

How should one proceed here? How do you connect the two devices together?

With KNX it would be relatively simple. It depends on which functions are to be covered. For example, in the simplest variant, one could create a few scenarios that could then be executed manually and also automatically.

What is the benefit of the joint control?