Single-family house, 1.5 stories, 155 sqm

That is normal, which is why good construction partners are so important - and conversations about "how do I want to live" instead of just the seemingly obvious "what should the house look like and what does which detail cost"

Exactly that should be the goal to find out. Of course, there are extremely sensible "constraints" that one should consider when building a house. But besides that, one should really be brave to trust one’s own feeling and individuality. In fact, nowadays it is all the more difficult to really find those for oneself, given all the diverse influences one is exposed to or exposes oneself to.
Question the supposed guideline that a south-facing location is best, for yourselves.

One should not forget that you sit outside 90% of the time in summer.

That is different for me, although I am a fresh-air person. When it is warm outside, I also like being indoors during the warm hours and let my air conditioner run lightly. Too much heat is unpleasant for me, just like rooms that are too warm. I would never lie in the sun while others like to sunbathe. My wife likes the sun but even she sits less directly in the sun.

So it is mainly about getting the light into the house with a north terrace.

That is exactly what I would do here as well.
For example, we love our large window areas, which make the living space feel significantly larger. We do not have a full south side, otherwise that might be a problem with the heating of the rooms and especially with the direct, glaring sunlight. In that respect, I find it again an advantage or at least a smaller disadvantage to have the north side for that.
Maybe you could also draw a plot plan for yourselves with those mentioned quiet or sunny corners so that you can imagine living in the house and outside as a whole. Up there could also be a really nicely looking garden shed with a lounge terrace, fridge, and coffee machine etc. for summer use.
If you mentally set aside the "usual suspects" standards with just one terrace at the house, trampoline, wire mesh fence etc. that you see elsewhere and play freely on your plot, you will find exciting solutions as well.

We have always been very focused on the south garden so far.

If you are unnecessarily fixated, it gets difficult and you are quickly disappointed. There is no reason for this fixation. You want to build on this property, so some things simply do not exist ... but in return, other things do.
With your latest floor plan, as a lover of open spaces, I could imagine the partition wall from hallway to living room being half-high; also with the seating furniture arrangement you mentioned, I would detach myself from the generally known and perhaps think of two small sofas or individual, light armchairs loosely arranged and not in the familiar 3-2-1 manner with TV in front. The windows could be adjusted accordingly.
What I haven’t fully understood yet are the different utility rooms that maybe could be combined. On the ground floor there would be technical and storage/work separated, on the upper floor a fairly large utility room (which could also include technical and storage options) and again storage/closet, which I would probably assign to the bedroom or use as a dressing room. If you actually plan the bathroom upstairs without a bathtub, it could also give up 1-2 sqm.

By the way, I also find the draft from #20 quite interesting. I can hardly understand your objections, but be that as it may.

If only because I haven’t raised any objections against this draft at all.
I merely recommended not to build a niche for the Wm/Tr tower, but to place it without such a special feature in the expanse of the utility room. I have nothing to object to the OP’s draft and don’t find it bad either, but consider yours just more inquiry-ready.

I definitely wouldn’t do that, because in my opinion it’s not even certain yet where the house will be placed.

What prevents you from already having a provider look for what they have in their portfolio similar to your draft?

Especially since this washing tower becomes a disaster at the latest when the machines have right-hinged doors. Then you are pressed into your corner.

Here is a preliminary draft, comparable in size

How easy it is to criticize and I hope that what I write is more helpful than overwhelming. I went through the "running routes" once. I noticed that the utility room can only be reached through the only bathroom. You always have to go through 2 doors with all the laundry, and if someone is in the bathroom, then you are either locked in or locked out – maybe not at first with children, but when they become teenagers, it will be a potential daily annoyance. You can also rotate the staircase 90 degrees if you keep the pantry underneath. That opens up a different rearrangement of the upper rooms. However, the approach by to plan the upper floor first and then the ground floor is certainly a better option than just rotating the staircase. The suggestion to bring light into the roof from above is valuable. Yes, the technical room appears too small for what is common today (heat pump, hot water tank, electricity storage). One consideration could be to move the technical room upstairs and the utility room downstairs. To reconcile the many requirements downstairs (generous living, working, technology or utility), I would consider movable walls and how different constellations ideally meet the respective requirements one way or another. This also makes much better use of the hallway space. If the idea seems too crazy to you, still play with the constellations. It frees your mind and space for new ideas. Sometimes something emerges that is quite obvious but not yet thought of.

Especially since this washing tower becomes a disaster at the latest when the machines have doors with right-hand hinges. Then you are pressed into your corner.

With most machines, you can now change the hinge with a few screws. We have a washing machine and dryer from AEG, now 7 years old. That was already possible then.

With most machines, you can now change the stop with a few screws.

And even if that's possible, the door hits the wall when opened ... so with the size of the room, you don't really need to create such a niche. Aside from that, I also agree with you regarding the positioning and access to the utility room. Confined spaces are usually not ideal.