5.5 hours of conversation. Diffusion open or closed?

I’m getting back in touch because the topic apparently wasn’t completely resolved after all. At least, I couldn’t find anything conclusive.

Since we want to build with diffusion openness, somehow only Keitel-Haus houses remain. All the others have installed a vapor retarder fleece.
Is this now problematic or not? One with this fleece is Fingerhaus, who also made a great impression on me and would be a close contender if it weren’t for this annoying fleece.

Vapor barrier does not mean that it is not diffusion-open, that's why it is called a barrier and not a seal. We have a barrier.

Is this now tragic or not?

IMHO quite clearly no, it is not tragic.

I only got around to calling a local provider today regarding solid construction, who said I first need to find an architect who then does a tender so that I can then commission the company and they can tell me what it will cost. But if I do that with a few, it will already cost me several hundred euros just for the information, right?

The company we are building with has its own planners who first work out a floor plan and create an offer. I believe only somewhat larger construction companies do that.