Primarily Vienna. There's nothing complicated about what Vienna did - other cities just prefer to please billionaires instead of providing services to citizens.
I didn't stay in social housing while I living there but I never once heard people complain about it. They basically just didn't think much about it at all and felt it was a good system and then would ask me why the US only makes it for poor people.
But you are right, that surplus housing is no longer a thing in Berlin.