Basics of wireless smart home solutions

I would like to add that there is also KNX-RF. :)

I would like to add that there is also KNX-RF. :)

Correct. But the effort for RF is similar to wired KNX and therefore significantly higher than for other wireless solutions that, at the end of the day, also open and close the blinds and switch the lights.

Once again: I still consider KNX to be the only true solution :)

I wouldn't say that as a general rule, but since radio solutions were asked about first, this is why the note was given.

I find it completely legitimate to install conventional electrical wiring with a switch program in a new building and retrofit it later as a "comfort layer" with radio solutions.
With radio, it would be important to know the "quasi-standard." Similar to music formats, where STEREO was and probably still is the most future-proof format, with radio it would be: Zigbee??? Enocean??? No idea, but it already helps if the radio signal is "standardized."
It is then also important to know the availability and compatibility of the actuators and central units. Likewise, the "software." I personally use a Raspberry Pi as "base hardware." Also with the background that in the future it will be easier to get replacement boards for this. Therefore, I would personally never use a NAS with virtualization etc. The guiding principle should also be here: "Keep it simple." For example, we have exhaust fans with built-in humidity sensors. At first, I absolutely wanted to control this myself, but now I am somehow "glad" that they turn on and off automatically. Regardless of whether a "central unit" is currently online or offline.
Only the idea of visualizing the status or actually switching manually could bring me to build a switching actuator in front of it.

I find it completely legitimate to install conventional electrical wiring with a switch program in a new building and to retrofit it later as a "comfort layer" with radio solutions.

That is roughly my approach and why I tend to prefer radio, fully aware that a BUS system is better. I want to start with simple things like centrally operable/programable roller shutters and lighting, then gradually see and consider which things make sense for me and then successively build a complete smart home. Many things are possible; whether I will need or even want them is another matter.

Which software do you use? I have already looked at ioBroker and IP Symcon and similar, I actually find the concept great, but I am unsure if I have enough time to really get into it.

If you are sure that you really want a smart home, I would always have an electrical installation suitable for it done.

Run everything to the switch cabinet and lay KNX cables, use electrical cables with 5 cores.

Then you can operate everything completely normally with switches (push buttons) and still make everything smart if you want.

However, then you also need a large box and/or sub-distributions.

Wireless is always problematic because of the range; some smart wireless parts can’t reach the room below from the first floor in my experience.

Concrete ceilings and closely laid underfloor heating cause significant interference.