In Paris, France, government officials went around the inner city area and forcefully removed all unofficial key safes from buildings. That’s how all cities should handle this.

However, some years ago there was a news story going around about one person that owns various different places in Berlin, all listed under different names on AirBnB and that person barely visits those places as he has cleaning people do everything in between bookings. They only pocket the huge amounts of money while doing nothing. And the description to find the door key was like “find the public bicycle rack and look for the broken bike with a pink frame, the key will be under the saddle” and there were specific instructions to not talk to anyone in that building. So they definitely knew that this was kind of a grey area…