Thanks for your answer!
You are right about the 24 Volt puls that is used to switch the relays, so NO constant 24 volt current is needed.
I Don't fully understand your provided solution with the switching without the relays on the Unipi …
Can you maybe make a little sketch of this setup?
It sounds like you would connect my buttons to both the DIN relays and the inputs on the Unipi.
So if I push a button, the light comes on (relay switches) and i get a 24 volt High input on the Unipi, so the Unipi knows the light is switched on.
But how would I switch the lamp trough the software, there needs to go a 24 volt puls from the Unipi to the relay right?
To bad the OpenHab people did not yet react to your offer ... it looks like a very good combination!
Lets hope they come around ...