Works just fine, I have 8000 BTU and it cools a living room very efficiently. I need it about one or two weeks per year in Finland. I can't imagine anybody working from home without one, even as north as Finland. Although we Finns are probably least used to heat so even 27 celsius is unbearable.

The only thing one needs is a window-sized cardboard with a round hole and blanket if your target room has no door. I just looked at prices and 10000BTU seemed to be ~350 euros.

I bought a portable split system for 2400 EUR. Works pretty well since I have shutters and a balcony, I put the external part outside the window, pull down the shutters and seal the lower part of the window around the pipe with some stuff. Doesn't use lots of power if I cool to 26C. Well, today we had 34C outside, so it had to work a lot.