Use lime, cement plaster, or gypsum plaster in the living area?

So I cook potatoes with the lid on the pot. The amount of steam coming from the vent hole is minimal. The similarity between that and showering is like between a broomstick and a bus.
Except for reducing something, nothing in a kitchen needs to produce steam amounts that would even remotely have anything to do with what happens in bathrooms. The thing with damp rooms and swelling gypsum plaster is nonsense.

The thing with the indoor climate, by the way, is nonsense too. No wall can do what a few nice plants can – just decorate with a few large devil's ivy spread around, and the good indoor climate is done. Plaster doesn’t matter.

I just say

Due to its versatility as well as its usage and processing advantages, gypsum plaster is used equally in residential and non-residential construction. Specifically in all kinds of interior spaces, including domestic kitchens and bathrooms. The latter are not considered wet rooms, but are explicitly classified according to DIN V 18550 Plaster and Plaster Systems – Execution as rooms with "normal air humidity," because moisture exposure to walls and ceilings there only occurs temporarily and only from splash water. With proper room use, gypsum plaster surfaces can be wet temporarily, but then also dry again without impairing the plaster.

The situation is quite different in actual wet rooms, such as commercial kitchens, swimming pools, or public shower rooms. Here, prolonged dampening of the surfaces can occur, which is why gypsum plaster should not be used. In an environment permanently exposed to water, the crystal structure of gypsum loses strength. This distinction between (commercial or public) wet rooms and domestic kitchens and bathrooms is made both in the aforementioned DIN V 18550 and in a number of technical datasheets, such as the datasheet on composite waterproofing systems.

If someone likes lime-cement, they are welcome to use it.

But I know from our interior bathroom with a shower that even after almost 20 years, the gypsum is still just as it was applied.

That's right. Bathrooms are only called wet rooms colloquially.
With 2 liters of steaming boiling water in the kitchen, I wouldn't panic either. Compared to a shower and the size difference of the rooms, I consider that irrelevant.

Rainshower pulls full throttle over 20 liters through. Actually a terrible trend.

I currently have two offers for interior plaster. Surcharge from gypsum to lime-cement per sqm once €4 and once €1.70 net.
Whereas 12 times more area with gypsum plaster is planned in the bill of quantities.

What a hair-splitting argument. Would have, could have, should have. Some people have their kitchen there just as decoration anyway, while in other households they cook twice daily for a family of five, 365 days a year. But that doesn’t matter. An open kitchen can be the cause of temporarily increased humidity, which can settle at thermal bridges elsewhere in the house. Gypsum plaster is more sensitive to moisture than lime-cement plaster, so what’s the point of the discussion? That doesn’t mean that tomorrow everyone’s gypsum plaster here has to swell, no one claimed that.

Gypsum plaster is cheaper, easier to work with, and looks better (matter of taste). If the moving helper gets stuck with the bulky floor lamp, gypsum plaster breaks faster, or a scratch is more noticeable on the smooth surface than on lime-cement plaster, which is typically worked more roughly. That also must not be forgotten.

This also comes from that side: someone has had concrete tiles on the roof for 50 years and is still very satisfied, while the neighbor replaced the clay tiles after only 40 years.

In our area, for example, cold-cement plaster is used as the base plaster in 95% of masonry houses. The top coat plaster with the desired grain size, e.g. 0.8mm/1mm/1.5mm/2mm (Scheibenputz), is applied on this base plaster; in the rarest cases, the plaster is finished smooth... which is probably more common with wooden houses... just putty, paint, done)
I have lime-cement plaster in the bathrooms, and pure lime plaster with a pure mineral top coat in all other rooms.