I have one at home and it won't be enough for a 100m2 flat to humidify it efficiently.... Not because I don't think it can do 100m2, the unit is really top (quiet, LEDs completely off etc.), they have thought about something. It's more likely that you can't ventilate several rooms in such a way that the humid air is evenly distributed and the sensor is of course on the unit itself and the room in which it is located will reach the desired value first and thus it switches off until the value drops again... And in continuous operation, the room in question will probably become a lot more humid. So it will be difficult, I think. I use it more to keep the air humid locally (now it's in the children's room), so I rarely have to add water.
But since the manufacturer himself seems to be answering questions here, he can certainly answer this better and perhaps make a recommendation.

I live in a Minergie flat, where the air is constantly circulated, which is why, in my opinion, you should oversize. This means that my bedroom and study, each 16 square metres, each have a normal Oscar. They both run near the door to the living room, which also gets some air. Dividing the performance (1 Oskar Big for 1 flat of 100 sqm with 4 rooms, for example) is not possible, as has already been explained here. The square metre performance is more of a guideline, whereby "big" is also meaningful: Oskar Big for big rooms, Oskar little for little rooms.

Very good answer swissroach! We are talking about 100m2 for one room. Oskar big has a very high output. However, this is limited by rooms that add up to 100m2 but are separated by walls. The desired humidity is first achieved in the room where Oskar big is placed. Among other things, the humidifier is very suitable for high and open rooms, e.g. open kitchen, living room. For single rooms we recommend Oskar up to 50m2 and Oskar little up to 30m2. We are also happy to answer your questions by phone: 041 720 48 48 :-)