As far as I know, this is actually allowed for existing buildings. Acquaintances from BW have even less in a half-timbered house (ownership and partially rented out).
2.2m seems quite low to me, but not totally dramatic. If it doesn’t bother you, then everything is fine. We also have only about 2.25m in a small hallway (about 2.6m in the rest of the house). My beloved 236cm Pax wardrobes just don’t fit in the hallway.
In any case, you have less space to heat and I was able to paint the ceiling in the mentioned hallway without a ladder.
Well, let's agree that it is definitely well below average. In the end, what really matters is whether you like it or not. Turn the flaw into a bonus for yourself and tell the seller that due to the low ceiling height, a total deduction of XXX is appropriate. It is still somewhat strange given the year of construction. Basement ceilings are usually insulated on the cold side, and underfloor heating should not actually add 20cm. How high are the ceilings on the upper floor?
That is true, however. I also find it strange that they renovated [das derart komisch], making the height on the ground floor so low, because normally you would apply the insulation on the basement ceiling and thus rather reduce the height of the basement ceiling than that of the ground floor. And underfloor heating is usually not that high, it does add a few centimeters, but not that much.
Turn the flaw into a bonus for yourself and tell the seller that due to the low ceiling height a total reduction of XXX is appropriate.
At the moment, as a home buyer, you are unfortunately being laughed at when you want to negotiate... I have been searching for over a year now and no house stays on the well-known portals for longer than 3 weeks before it is gone. Even if, from my point of view, it is almost junk. I would now estimate the window sill height to be around 1.10 - 1.30 m.