Welcome to the bureaucracy loop that you’ll need to face if you ever plan on leaving Germany.
Let me make you a drawing first:
Bonus question: How many loops do you see here?
From what I’ve been told, this landlord letter requisite was a law approved in 2015 in order to decrease german bureaucracy… I guess we can call that a fail; now realize that you can only cancel your accounts or subscriptions after you have the bureau official document that you are leaving Germany.
Yes, this is “The Loop” of leaving Germany, very similar to the one that you’ll go through when you arrive in, where you need to register at the bureau with a valid address, and you need a bureau official document to rent a house to have an official address.