New build - which SmartHome system?

That's how it looks. You haven't quite understood what it's about and how it all connects.

As the top layer, you can take whatever comes to mind. Whether it's just [Mygekko], [Homekit], [Homeserver], [IP-Symcon] and so on... or various other open-source projects.

But without [ETS] you can't get the engine running in the first place.

Or in other words: [Mygekko] is the operating system in this case and [ETS] is the BIOS. Without it, you simply won't get far, no matter what operating system you want to use and no matter how great it may be. After that, once the computer has started, you can do whatever comes to mind.

I am still in the planning phase for the upcoming single-family house and felt the same way. Do yourself a favor and go for KNX, you don’t have to integrate everything right from the start, just lay enough cables for the most important parts to retrofit desired actuators/sensors later. I personally got the ETS last year in a group purchase with a 40% discount, so it costs about €700. I do all the KNX configuration myself, which is the best way to learn, and I can expand everything myself later on.

Regarding configuration/logic in general, with KNX you don’t program any server etc. with logic but the light switch itself. A small example: living room with 6 push buttons, here you configure the button itself and not the modules in the control cabinet or anything else.
If you want nice comfort functions later, check out iobroker, it’s free and you can create nice logic with Blockly etc., and most importantly the basic KNX functions remain intact!

But keep in mind you want more over time, a small example of how I approach it -> MDT glass push button in the large living/dining area. At first, only light on/off and roller shutter up/down will be programmed here. When you live in it and have time, you can program nice things like scenes, different levels, radio/music over the ceiling speakers etc. on the side. Handing this over to an external person and gradually having your wishes programmed would surely cost more than the ETS license in the long run.

There are also comparisons of various smart home systems and their costs online. In the end, they don’t differ much, but with KNX you have the most options. Just the MDT glass push button (yes, I’m a fan), 6 buttons, several levels, illuminated (dimmable), temperature and light sensor, digital display, nice design for about €140.

Have you ever looked at Loxone?

I don't think much of KNX in private households

Regards Patrick

Loxone? You mean the proprietary system that likes to discontinue interfaces, requires expensive network cables, expensive actuators, and ugly, non-intuitive buttons?

SCNR

Compared to KNX, generally still more expensive to purchase. Of course, if you want to have the same functionality. We have had (not only) here in the forum several comparison offers where the choice then still fell on KNX because it is cheaper.

Why should one even say a word about it then?

I don't think much of KNX in private households

Why?