Which internet solution do you recommend?

Well, 8k streams do exist and have peaks over 50 MBit/s. Of course, compression is used, but that's not a big deal. I don't think you have to see the end of copper right away. The in-house wiring won't be the bottleneck for quite a while, if ever. For Dolby Atmos, you mainly need suspended ceilings and walls to be able to integrate the maximum number of speakers. Putting Atmos on 5.1, 7.1, or 9.1 is nice, but misses the point. So the copper cable is the smallest problem. Per LAN, per access point per floor.

8k streams... from the net or what? Like 4k on YouTube? That's all not comparable and far from practical... on YouTube, moreover, with an insanely poor quality. Have you ever seen 4k YouTube and "real" 4k on a 4k TV? There's worlds between them! It has to be that way... because otherwise, no one in the third-world country Germany would be able to stream 4k YouTube.

For example, I streamed The Hobbit in 3D/HD as a Blu-ray ISO here... Peak 110mbit/s. The NAS is about 30 meters cable length away... with a 100 mbit network I couldn't get it to run smoothly. I'm always talking about streaming over the network! Not about playing from a player on the TV! The data volume of 8k is 16 times as large. With various 4k movies, I have a peak of >300mbit.

The cable has at least 1,000 MBit... and as soon as you do more than just surfing the internet and watching a bit of TV, you will run into problems. You can forget about a NAS with dLAN.

Then you’re a bit flexible and lay a LAN cable behind the baseboard.

What problems people have these days. When I think back to my early internet days, I laid a telephone cable from the ground floor through the stairwell to the top floor and connected my 9600 modem there. Apart from that, if it turns out to be impossible to use the carefully chosen desk location in the children's room, you can always use the dLAN solution inside the kids' room as an emergency solution or simply the aforementioned Wi-Fi throughout the entire top floor.

What problems there are today. When I think back to my early internet days, I ran a telephone cable from the ground floor through the stairwell to the attic and connected my 9600 modem there. Apart from that, if it should be impossible to use the previously carefully chosen spot for the desk in the children's room, you can always use the dLAN solution within the KZ as an emergency solution or the said WiFi throughout the entire attic.

What problems there are today. My great-great-great-grandmother still had to hitch the horses to the wagon before going to town. And today everyone just gets into the car...lazy lot...

What problems there are nowadays. My great-great-great-grandmother always had to harness the horses to the carriage before going to town. And today everyone just gets in the car... lazy bunch...

I didn't mean to bring back "the good old days" but I don't understand why CAT cables aren't simply installed in every room. In terms of effort, it's absolutely manageable and the simplest and by far most sensible solution.

.... that you don't just run CAT cables into every room.

A brief OT from a layman: are CAT cables really so sensitive that special care must be taken when laying them? Rhineland greetings

I’m not an expert either, but the more data that has to go through there, the better it needs to be shielded and installed. Cat5 is quite unproblematic in my opinion, Cat7 is more demanding.