I would have expected this wall to be one centimeter thinner; that would fit with (in a grid of reinforcing bars) vertically built bricks. Occasionally, plasterboard walls were also used for such applications. I expect the ceiling beams here to run from top left to bottom left in the plan.
The wall consists of hollow bricks, in a single row. There are no iron reinforcements installed. At the neighbors' place, the entire wall actually just fell down when they had only removed a part of it. When we installed new electrical wiring back then, I simply came out on the other side ^^, the wall is that thin.
The beams apparently run in this floor or at least in the living room from left to right in the plan — on the upper floor they run as you described. So, on the ground floor they run perpendicular to the vault. We once opened a piece of floor in the living room at the height of a peak of a vault arch to see how much space we have at the lowest point for insulation and underfloor heating. Above the peak, up to the top edge of the old floorboards was about 14 cm of space. Up to the top edge of the current floor, just under 16 cm. We still have a little room upwards if necessary.
We thought about it back and forth over the weekend and then came to the conclusion that the simplest and most effective solution is the following:
This way, a 1.5m Pax with 236 cm height and 60 cm depth would fit in there as a large, sufficient hallway closet. A recess of up to 40 centimeters is possible without having to change anything in the kitchen. We want to keep the table. The shoe cabinet could then go away, and finally, there would be more space to walk, put on shoes, etc.