You need the owners permission. In the specific case of a building where different people own different apartments, that's the owners assembly for the outside. That's not the same as it being forbidden by regulations, and not particularly specific to European countries. Fairly sure if you own a condo in the US they'll also have their own rules about what you are allowed to do to parts of the building outside your unit and a voting process for exceptions and changing it.

And obviously ownership law like that has nothing to do with "greenwashing propaganda".

Some areas can have local restrictions facade design, but that's neither universal nor something that can't be mitigated.

That's not true at all. Individual or terraced houses are not "common property" and owners are free to install what they want.

Apartments buildings with multiple owners are governed by a "syndic" that is comparable to American HOAs (as far as I understand HOAs) and they can put restrictions on AC installations if a majority of owners agree. Usually the most annoying part is that you need to wait a couple of weeks for permission to drill through the exterior wall (which is common property obviously).